JP2015186087A - Measuring device, control device, measuring method, and control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to measure delay time difference among a plurality of networks even if a watch comprised in a transmission side device and a watch comprised in a reception side device are asynchronous.SOLUTION: A derivation unit 44 obtains first clock time when a radio device 10 transmitted a first signal to a communication device 18 via a first network, and second clock time when the communication device 18 received the first signal. The derivation unit 44 obtains third clock time when the radio device 10 transmitted a second signal to the communication device 18 via a second network, and fourth clock time when the communication device 18 received the second signal. The derivation unit 44 derives relative transmission delay difference between the first network and the second network on the basis of the first clock time, second clock time, third clock time, and fourth clock time.

Description

  The present invention relates to communication technology, and more particularly to a measurement device, a control device, a measurement method, and a control method that transmit signals via a plurality of networks.

  When video / audio by live streaming is transmitted via a communication network such as the Internet, quality assurance for the communication path becomes an issue when the best effort method is used. In order to cope with this, when the quality of streaming via the Internet is lowered, the line is switched to a line whose quality is guaranteed, that is, a line with good quality (for example, see Patent Document 1).

JP 2004-72182 A

  When streaming video captured by an imaging device such as a camera as live video, the transmission delay time may vary depending on the connected Internet service provider. In order to perform live streaming transmission, a network with a short delay time and sufficient throughput is required. In order to measure the delay time, it is necessary that the clocks of the transmitting device and the receiving device are synchronized. However, in order to reduce the manufacturing cost of the device and the operating cost of the system, the highly accurate synchronization means of the watch is omitted.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide communication between a plurality of networks even if a clock provided in a transmission-side device and a clock provided in a reception-side device are asynchronous. It is an object of the present invention to provide a technique for measuring the delay time difference between the two.

  In order to solve the above problems, a measurement device according to an aspect of the present invention includes a first acquisition unit that acquires a first time at which a transmission device transmits a first signal to a reception device via a first network, and the reception device. A second acquisition unit that acquires a second time at which the first signal is received, a third acquisition unit that acquires a third time at which the transmission device transmits the second signal to the reception device via the second network, and reception. A fourth acquisition unit that acquires a fourth time at which the device receives the second signal; a first time acquired by the first acquisition unit; a second time acquired by the second acquisition unit; and a second acquisition acquired by the third acquisition unit. And a derivation unit for deriving a relative transmission delay difference between the first network and the second network based on the third time and the fourth time acquired by the fourth acquisition unit. The first time and the third time are timed by the clock at the transmission device, and the second time and the fourth time are timed by the clock at the reception device.

  Another aspect of the present invention is a control device. The apparatus includes (1) a first time when the transmitting apparatus transmits a first signal to the receiving apparatus via the first network, (2) a second time when the receiving apparatus receives the first signal, and (3) a transmitting apparatus. Is the third time when the second signal is transmitted to the receiving device via the second network, and (4) the transmission delay difference derived based on the fourth time when the receiving device receives the second signal, An acquisition unit that acquires a relative transmission delay difference between the first network and the second network and a transmission device that transmits a signal to the reception device based on the transmission delay difference acquired by the acquisition unit. And a determination unit that determines the first network or the second network as a route. The first time and the third time are timed by the clock at the transmission device, and the second time and the fourth time are timed by the clock at the reception device.

  Yet another embodiment of the present invention is a measurement method. The method includes: obtaining a first time at which the transmitting device has transmitted a first signal to the receiving device via the first network; obtaining a second time at which the receiving device has received the first signal; Obtaining a third time at which the device has transmitted the second signal to the receiving device via the second network; obtaining a fourth time at which the receiving device has received the second signal; and obtaining the first time; Deriving a relative transmission delay difference between the first network and the second network based on the acquired second time, the acquired third time, and the acquired fourth time. The first time and the third time are timed by the clock at the transmission device, and the second time and the fourth time are timed by the clock at the reception device.

  Yet another embodiment of the present invention is a control method. This method includes (1) a first time when the transmitting device transmits a first signal to the receiving device via the first network, (2) a second time when the receiving device receives the first signal, and (3) a transmitting device. Is the third time when the second signal is transmitted to the receiving device via the second network, and (4) the transmission delay difference derived based on the fourth time when the receiving device receives the second signal, And a step of acquiring a relative transmission delay difference between the first network and the second network, and a path when the transmission device transmits a signal to the reception device based on the acquired transmission delay difference. Determining a first network or a second network. The first time and the third time are timed by the clock at the transmission device, and the second time and the fourth time are timed by the clock at the reception device.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to measure a delay time difference between a plurality of networks even when a clock provided in a transmitting device and a clock provided in a receiving device are asynchronous.

It is a figure which shows the structure of the delivery system which concerns on Example 1 of this invention. It is a figure which shows the structure of the radio | wireless apparatus of FIG. FIGS. 3A and 3B are diagrams showing signal formats used in the distribution system of FIG. It is a figure which shows the operation | movement outline | summary in the derivation | leading-out part of FIG. It is a figure which shows another operation | movement outline | summary in the derivation | leading-out part of FIG. It is a figure which shows another operation | movement outline | summary in the derivation | leading-out part of FIG. It is a figure which shows the outline | summary of the packet distribution operation | movement in the delivery system of FIG. It is a figure which shows the structure of the communication apparatus of FIG. It is a sequence diagram which shows the path | route switching procedure by the delivery system of FIG. It is a sequence diagram which shows another route switching procedure by the delivery system of FIG. It is a figure which shows the structure of the delivery system which concerns on Example 2 of this invention. It is a figure which shows the structure of the delivery system which concerns on Example 3 of this invention.

(Example 1)
Before describing the present invention specifically, an outline will be given first. Embodiment 1 of the present invention relates to a distribution system for transmitting a signal from a transmission device to a reception device while switching the network between the transmission device and the reception device connected via a plurality of networks configured in parallel. . In such a distribution system, for example, a transmission device performs streaming distribution of moving image data generated by imaging to a reception device. In such a case, a network with a short delay time in transmitting a signal should be selected. This selection requires measurement of the delay time for each network. Furthermore, as described above, it is required to measure the delay time in a situation where the clock provided in the transmission device and the clock provided in the reception device are asynchronous.

  However, when the delay time becomes long, it is not realistic to interrupt the live streaming transmission, connect to another Internet service provider, and restart the live streaming transmission to check the delay time. In the case of a usage method in which stream transmission is performed while moving, the delay time and throughput may also vary. Further, when switching to another communication path, it is required to reduce the load on the device when measuring the delay time of the switching destination. However, a measurement that is confirmed by transmitting a signal as much as the bit rate of streaming increases the load on the device.

  In view of this, the purpose of this embodiment is to compare the delay times of networks when they are asynchronous. Another object of the present invention is to monitor the amount of delay and throughput that vary during streaming, automatically select an optimum network from a plurality of networks without interrupting the stream, and perform path switching. In this embodiment, the shorter delay time is selected by measuring the delay times for each of the two paths and comparing them.

  FIG. 1 shows a configuration of a distribution system 100 according to the first embodiment of the present invention. The distribution system 100 includes a wireless device 10, a first base station device 12a, a second base station device 12b, collectively referred to as a base station device 12, and a first network 14a, a second network 14b, and a third network, collectively referred to as a network 14. 14c, the fourth network 14d, the Internet 16, and the communication device 18.

  The wireless device 10 is connected to an imaging device (not shown) and receives a signal including moving image data from the imaging device. The wireless device 10 corresponds to the transmission device described above. The wireless device 10 corresponds to two networks and performs communication via each network. Here, it is assumed that the combination of the first base station apparatus 12a and the first network 14a and the combination of the second base station apparatus 12b and the second network 14b are different radio communication systems. Since the wireless device 10, the base station device 12, and the network 14 execute processing according to the rules of a known wireless communication system, description thereof is omitted here. The network 14 may be an Internet service provider. Hereinafter, a combination of the first base station apparatus 12a and the first network 14a may be simply referred to as a first network 14a, and a combination of the second base station apparatus 12b and the second network 14b may be simply referred to as a second network 14b. is there.

  The Internet 16 is connected on the one hand to the first network 14a and the second network 14b, and on the other hand to the third network 14c and the fourth network 14d. The third network 14c and the fourth network 14d are wired communication systems. The third network 14c and the fourth network 14d are, for example, different Internet service providers. The communication device 18 is connected to the third network 14c and the fourth network 14d, and receives a signal from the wireless device 10 via at least one of them. The communication device 18 reproduces moving image data by processing the received signal. The communication device 18 corresponds to the above-described receiving device.

  In such a configuration, signal transmission, that is, the above-described streaming transmission is performed, for example, through the following route. The signal is transmitted from the wireless device 10 to the Internet 16 via the first base station device 12a and the first network 14a. Further, the signal is received by the communication device 18 via the third network 14c. At that time, for example, the first network 14a is appropriately switched to the second network 14b in accordance with the delay time and throughput.

  FIG. 2 shows the configuration of the wireless device 10. The wireless device 10 includes an encoder 30, a streaming protocol control unit 32, a transmission control unit 34, a communication unit 36, a first communication unit 36a, a second communication unit 36b, a measurement control unit 38, a measurement device 40, and a control device. 42. The measurement device 40 includes a derivation unit 44, and the control device 42 includes a determination unit 46. Here, the description will focus on functions related to transmission, and description of functions related to reception will be omitted.

  The encoder 30 inputs moving image data from an imaging device (not shown). The moving image data is a result of converting a moving image captured by the imaging apparatus into digital data. The encoder 30 performs encoding on the input moving image data. A known technique may be used for encoding, but as an example, MPEG2-TS (Moving Picture Experts Group-2 Transport Stream) may be used. The encoder 30 outputs the encoded moving image data (hereinafter also referred to as “moving image data”) to the streaming protocol control unit 32.

  The streaming protocol control unit 32 inputs the moving image data from the encoder 30. The streaming protocol control unit 32 executes processing corresponding to the streaming protocol on the moving image data. Since a known technique may be used for the streaming protocol, a description thereof is omitted here. The streaming protocol control unit 32 outputs moving image data (hereinafter also referred to as “moving image data”) that has been subjected to processing corresponding to the streaming protocol, to the transmission control unit 34.

  The transmission control unit 34 receives the moving image data from the streaming protocol control unit 32 and stores the moving image data in a packet. The transmission control unit 34 outputs the packet to the first communication unit 36a or the second communication unit 36b. Here, the output destination of the packet is designated by the determination unit 46. The transmission control unit 34 may output a packet to the two communication units 36 when switching the output destination communication unit 36. The communication unit 36 corresponds to different wireless communication systems and executes communication processing corresponding to each wireless communication system. As described above, since the wireless communication system is a known technique, the description thereof is omitted here. The communication unit 36 receives the packet from the transmission control unit 34 and transmits the packet.

  The measurement control unit 38 controls measurement processing for examining the delay time and throughput of the transmission path with the communication device 18 (not shown). The measurement control unit 38 periodically transmits a measurement request packet from the communication unit 36 toward the communication device 18. The measurement request packet is a packet for delay measurement and throughput inquiry. Thereafter, the measurement control unit 38 receives the measurement result from the communication device 18 via the communication unit 36 as a measurement response packet.

  FIGS. 3A and 3B show examples of signal formats used in the distribution system 100. FIG. FIG. 3A shows the format of the measurement request packet. The transmission side interface identification number indicates a number for identifying the first communication unit 36a or the second communication unit 36b to which the measurement request packet is to be transmitted. The transaction number is a number for linking a measurement request packet and a measurement response packet described later. The same transaction number is assigned to the corresponding measurement request packet and measurement response packet. The packet transmission time indicates a time at which a packet should be transmitted from the first communication unit 36a or the second communication unit 36b. The packet transmission time is measured by a clock built in the wireless device 10. The transmission bit rate is acquired from the transmission control unit 34.

  FIG. 3B shows the format of the measurement response packet. The receiving side interface identification number is the third communication unit 36c or the fourth communication unit 36d provided in the communication device 18 described later, and the third communication unit 36c or the fourth communication unit 36d that should receive the measurement request packet. Indicates a number for identifying. The packet reception time indicates the time when the measurement request packet arrives at the communication device 18, and the reception bit rate indicates the bit rate of the packet being received through the same route as the route through which the measurement request packet is transmitted (average over a certain unit time). Indicates. The packet reception time is measured by a clock built in the communication device 18. Here, the timepiece built in the wireless device 10 and the timepiece built in the communication device 18 are asynchronous. Returning to FIG. The measurement control unit 38 outputs the packet transmission time and the packet reception time to the derivation unit 44. The measurement control unit 38 may output the bit rate to the derivation unit 44.

  The deriving unit 44 inputs the packet transmission time and the packet reception time from the measurement control unit 38. That is, the packet transmission time (hereinafter referred to as “first time”) when the wireless device 10 transmits the measurement request packet to the communication device 18 via a predetermined network is acquired. Further, the deriving unit 44 acquires a packet reception time (hereinafter referred to as “second time”) when the communication device 18 receives a measurement request packet via a predetermined network. In addition, the derivation unit 44 acquires a packet transmission time (hereinafter referred to as “third time”) when the wireless device 10 transmits the measurement request packet to the communication device 18 via another network. Further, the deriving unit 44 acquires a packet reception time (hereinafter referred to as “fourth time”) when the communication device 18 receives a measurement request packet via another network. As described above, the first time and the third time are measured by the clock in the wireless device 10, and the second time and the fourth time are measured by the clock in the communication device 18.

  The predetermined network corresponds to, for example, a network obtained by combining the first network 14a and the third network 14c in FIG. Another network corresponds to, for example, a network in which the second network 14b and the third network 14c are combined in FIG. In the case of FIG. 1, there is also a network in which the fourth network 14d is combined, so there are two types of remaining networks, and there are a total of four types of networks. Here, for clarity of explanation, the processing for the two types of networks described first will be described, and the processing for the remaining two types of networks will be omitted. However, the processing described later may be executed for the remaining two types of networks.

The deriving unit 44 derives a relative delay difference between the predetermined network and another network based on the first time, the second time, the third time, and the fourth time. FIG. 4 shows an outline of the operation in the derivation unit 44. In general, when trying to measure the delay amount of packet transmission due to a communication path between devices installed at distant points, the clocks of the devices need to be synchronized with high accuracy. However, since the relative delay difference between the paths is measured here, it is not always necessary, and it is only necessary to have sufficient accuracy of the individual clocks for comparing the delay amounts. The arrow extending horizontally to the right of the “wireless device clock C _S ” in FIG. 4 represents the passage of time, and the arrow direction is the future side. The same applies to the arrow extending to the right of the “communication device clock C _R ”.

When sending measurement request packet from the first communication unit 36a, the time t _sA during measurement request packet transmission, is timed by the clock C _S of the wireless device 10, the measurement control unit 38, and stores it in the measurement request packet . On the other hand, when the measurement request packet is transmitted from the second communication unit 36b, the time t _sB at the time of transmission of the measurement request packet is stored in the measurement request packet. When the communication device 18 receives the measurement request packet from the first communication unit 36a via the third network 14c by the third communication unit 36c described later, the measurement control unit 68 described later communicates the received time. It is stored as the time _{t rA} measure by the clock _{C R} of the device 18. Similarly, when the communication device 18 receives the measurement request packet from the second communication unit 36b, the measurement control unit 68 described later stores the received time as _trB . Here, the time _{t sA} corresponds to the first time, the time _{t sB} is equivalent to the third time, the time _{t rA} corresponds to a second time, the time _{t rB} corresponds to the fourth time.

The deriving unit 44 uses the time t _sA , the time t _sB , the time t _rA , and the time t _rB to use the first network 14 a, the Internet 16, and the third network 14 c as routes (hereinafter referred to as “route A”). The difference in delay amount from the route of the second network 14b, the Internet 16, and the third network 14c (hereinafter referred to as “route B”) is calculated as follows.
[Transmission time difference between the first communication unit 36a and the second communication unit 36b of the wireless device 10]
Δt _s = t _sB −t _sA
[Reception time difference at the third communication unit 36c of the communication device 18]
△ _t r _{= t} rB _{-t rA}
[Delay time difference between route A and route B] = Δt _r −Δt _s

FIG. 5 shows another operation outline in the derivation unit 44. Time t _sA , time t _sB , time t _rA , and time t _rB in the figure are the same as in FIG. Here, the calculation order for deriving the delay time difference between the route A and the route B is different from that in FIG.
[Transmission time from first communication unit 36a of wireless device 10 to third communication unit 36c of communication device 18]
Δt _A = t _rA −t _sA
[Transmission time from second communication unit 36b of wireless device 10 to third communication unit 36c of communication device 18]
Δt _B = t _rB −t _sB
[Delay time difference between route A and route B] = Δt _B −Δt _A

  FIG. 6 shows still another operation outline in the derivation unit 44. This corresponds to the case where the measurement method in FIG. 4 or 5 is applied to four routes (route A to route D). “Route C” is a route of the first network 14a, the Internet 16, and the fourth network 14d, and “Route D” is a route of the second network 14b, the Internet 16, and the fourth network 14d. If the measurement request packet is transmitted to all the routes, the relative difference of all the delay amounts can be obtained by the same calculation as described above. As a result, it becomes clear which route has the least transmission delay. In addition, about the relative difference of delay amount, it may measure several times and an average value may be derived | led-out. In this way, even if the clocks of the wireless device 10 and the communication device 18 are not synchronized with high accuracy, it is possible to check which route can be transmitted with the least delay. Returning to FIG. The deriving unit 44 outputs the derived time difference to the determining unit 46.

  The determination unit 46 acquires the delay difference from the derivation unit 44. The determination unit 46 determines a predetermined network or another network as a path when the wireless device 10 transmits a signal to the communication device 18 based on the acquired delay difference. If the determined network is different from the network already used, the determination unit 46 instructs the transmission control unit 34 to switch the network. For example, when the delay difference or the amount of decrease in the bit rate exceeds a threshold value, the determination unit 46 determines network switching. Alternatively, the delay amount and the bit rate may be weighted and weighted, and the threshold value may be compared. Furthermore, the determination unit 46 may select a network with a smaller delay time.

  FIG. 7 shows an outline of the packet distribution operation in the distribution system 100. When the decision unit 46 decides to switch to a route with a small delay amount, the transmission control unit 34 moves to a stream transmission route switching operation. Here, an example of switching from route A to route B is shown. A problem when switching from the path A to the path B is that, when transmitting the current stream to the path B as the switching destination, it is not known until there is sufficient throughput. Therefore, the transmission control unit 34 performs switching while confirming the throughput of the path B by dividing the stream in stages and gradually changing the ratio.

  In the stream packet, a sequence number is inserted as a header in the payload portion of each packet. Such a configuration is adopted, for example, in RTP (Real-time Transport Protocol). The sequence number is given as a monotonically increasing number when packetizing streaming data. When switching the stream to another path, a part of the packet with the sequence number inserted is transmitted to the switching destination path, and the communication device 18 reads the sequence number in the packet and rearranges it in order to restore the stream. To do.

  As an example, in FIG. 7, the transmission control unit 34 transmits four packets to the route A among the five stream packets and transmits one packet to the route B, thereby distributing the transmission route. The reception control unit 60 in the communication device 18 restores the stream by arranging packets received from the route A and the route B in order according to the sequence number. Further, the transmission control unit 34 uses the measurement request packet and the measurement response packet that are periodically performed, and gradually transmits to the path B while confirming whether or not the communication apparatus 18 has received the path B at a predetermined bit rate. Increase the ratio to do. When all streams are finally transmitted to route B, route switching is completed.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 8 shows the configuration of the communication device 18. The communication device 18 includes a third communication unit 36c, a fourth communication unit 36d, a reception control unit 60, a streaming protocol control unit 62, a streaming buffer 64, a decoder 66, and a measurement control unit 68, which are collectively referred to as the communication unit 36. .

  The third communication unit 36c is connected to the third network 14c, and the fourth communication unit 36d is connected to the fourth network 14d. Therefore, unlike the first communication unit 36a and the second communication unit 36b, the third communication unit 36c and the fourth communication unit 36d correspond to the wired communication system and execute communication processing corresponding to the wired communication system. Since the wired communication system is a known technique, the description thereof is omitted here. For example, the third network 14c and the fourth network 14d correspond to different Internet service providers. The communication unit 36 receives a packet from the network 14 and outputs the packet to the reception control unit 60.

  The reception control unit 60 receives the packet from the communication unit 36, extracts moving image data from the packet, and outputs the moving image data to the streaming protocol control unit 62. The moving image data corresponds to streaming data. The streaming protocol control unit 62 receives the moving image data from the reception control unit 60. The streaming protocol control unit 62 performs processing corresponding to the streaming protocol control unit 32 and processing corresponding to the streaming protocol on the moving image data. The streaming protocol control unit 62 outputs the processed moving image data (hereinafter also referred to as “moving image data”) to the streaming buffer 64.

  The streaming buffer 64 receives the moving image data from the streaming protocol control unit 62. When a route is switched between routes with different delay amounts or when a stream is divided and transmitted through a plurality of routes, it is necessary to absorb the difference in the delay amount somewhere. Here, the streaming buffer 64 absorbs the difference in delay amount. The timing for adjusting the delay amount is started when a path switching request is received from the wireless device 10, and when the adjustment is completed, a route switching preparation completion is transmitted to the wireless device 10. The delay amount adjustment is performed so that the decoder 66, which will be described later, is played back a little earlier or is played back a little later so that it is not noticeable. These controls are performed by the reception control unit 60. When a stream is switched from a path with a large delay amount to a path with a small delay amount, the delay amount is adjusted to that of a small path when the stream is completed. The streaming buffer 64 outputs the moving image data to the decoder 66. The decoder 66 decodes the moving image data from the streaming buffer 64. Decoding is performed so as to correspond to encoding by the encoder 30. The decoder 66 outputs the decoding result.

  The measurement control unit 68 receives a measurement request packet from the wireless device 10 via the third communication unit 36c or the fourth communication unit 36d. The measurement control unit 68 stores the arrival time of the packet, that is, the packet reception time. As described above, the reception time is measured by the clock provided in the communication device 18. At that time, the same communication unit 36 receives the streaming packet and the measurement request packet together. However, in the case of TCP / IP (Transmission Control Protocol / Internet Protocol) or UDP / IP (User Datagram Protocol) used in the Internet 16, the port number is specified as a different number in the measurement request packet and the streaming packet. Therefore, it can be sorted at the time of reception. Further, the measurement control unit 68 stores the stored packet reception time in the measurement response packet. The measurement control unit 68 returns a measurement response packet to the wireless device 10 from the third communication unit 36c or the fourth communication unit 36d.

The operation of the distribution system 100 configured as above will be described. FIG. 9 is a sequence diagram showing a route switching procedure by the distribution system 100. This shows a sequence example in which the path switching is normally terminated from the start of the path switching and in the case of being canceled halfway. The wireless device 10 transmits a path switching request to the communication device 18 (S10). Thus, the communication unit 36 used for transmission / reception among the plurality of communication units 36 is notified, and the communication device 18 is requested for preparation. The following is an example of the message, which is described in a character string in the payload of the communication packet.
PATHCTL / 1.0
msg: change-path-req
msgid: 123456
device-type: sender
deviceid: 987654
sender-if: 1
receiver-if: 2

  “PATHCTL / 1.0” indicates a control protocol and version number, “msg: change-path-req” indicates that the message type is a path change request, and “msgid: 123456”. Indicates the identification number of the message. “Device-type: sender” indicates the type of the device, “deviceid: 987654” indicates a unique number or character string for identifying the device, and “change-from-if: 1” indicates the route. "Change-to-if: 2" indicates the communication unit 36 (communication device 18 side) to which the path is switched.

When receiving the path switching request, the communication device 18 transmits an ACK for notifying that the request has been accepted (S12). The following is an example of the message.
PATHCTL / 1.0
msg: ack
msgid: 123456
device-type: receiver
deviceid: abcd123

  The communication device 18 prepares to receive a stream with the communication unit 36 designated from the wireless device 10, and when this is completed, transmits a message indicating completion of switching preparation to the wireless device 10 (S14). The wireless device 10 returns an ACK indicating that this message has been accepted (S16). Further, the wireless device 10 performs a path switching operation. When the path switching is completed, the wireless device 10 transmits a path switching completion message to the communication apparatus 18 (S18). The communication device 18 returns ACK (S20), and the path switching ends.

  However, when the switching destination path has insufficient throughput, switching may be stopped for some reason. In this case, the wireless device 10 transmits a message for starting the path switching stop to the communication device 18 (S22). The communication device 18 returns ACK (S24), and the path switching is stopped. When the route switching cancellation process is completed, the wireless device 10 transmits a route switching cancellation completion message to the communication device 18 (S26). The communication device 18 returns an ACK (S28). When the wireless device 10 receives an ACK from the communication device 18, the stop sequence is completed. The communication device 18 stops receiving the stream from the designated switching destination interface.

  FIG. 10 is a sequence diagram showing another route switching procedure by the distribution system 100. If you try to switch the route because the throughput of the stream transmission path is originally insufficient, even if the throughput of the switching destination path falls below the bit rate of the stream, there are two alternatives to canceling and returning to the original path. It may be better to divide the stream into (or more) (or more) paths for transmission. In such a case, when the transmission ratio of the stream is gradually shifted from the switching source path to the switching destination path, control is performed to balance the stream in the middle. FIG. 10 corresponds to this case.

  Steps 40 to 46 are the same as steps 10 to 16 in FIG. Based on the bit rate of the stream received by the communication device 18 based on the measurement request packet, the wireless device 10 determines that the throughput of the switching destination path is insufficient and the stream cannot be completely switched. In this case, the radio apparatus 10 determines the stream bit rate to be transmitted to each path from the ratio of the throughput capacity of the switching source path and the throughput capacity of the switching destination path. Then, the bit rate for transmission in each path is fixed at the ratio. The wireless device 10 transmits a message (divided transmission notification) notifying that the divided transmission state has been entered to the communication device 18 (S48). The communication device 18 returns an ACK (S50).

  According to the embodiment of the present invention, since the relative time difference between the two networks is derived, the delay time can be measured even if the clocks provided in each of the two devices are asynchronous. In addition, since the route is determined based on the delay difference, a route with a short delay difference can be determined. In addition, it is possible to automatically select a communication line having an optimum delay amount without any user operation and to switch without stopping the streaming.

(Example 2)
Next, Example 2 will be described. As in the first embodiment, the second embodiment also relates to a distribution system that transmits a signal from a transmission device to a reception device. The wireless device according to the first embodiment includes a control device and a measurement device. On the other hand, the wireless device according to the second embodiment includes a control device, and the communication device includes a measurement device. The distribution system according to the second embodiment is the same type as that in FIG. Here, it demonstrates centering on the difference with Example 1. FIG.

  FIG. 11 shows a configuration of a distribution system 100 according to the second embodiment of the present invention. The wireless device 10 includes a control device 42, and the communication device 18 includes a measurement device 40. The measuring device 40 in the communication device 18 derives the time difference as before. The communication device 18 transmits the derived time difference to the wireless device 10. Here, the derived time difference may be stored in the measurement response packet, or may be stored in a different packet. The control device 42 in the wireless device 10 determines a network based on the derived time difference.

  According to the embodiment of the present invention, since the delay difference is derived in the communication device, the processing amount of the wireless device can be reduced. In addition, since the control device and the measurement device are arranged separately for the wireless device and the communication device, the degree of freedom in design can be improved.

(Example 3)
Next, Example 3 will be described. The third embodiment also relates to a distribution system that transmits a signal from a transmission device to a reception device, as before. The wireless device according to the second embodiment includes a control device, and the communication device includes a measurement device. On the other hand, the communication device according to the third embodiment includes a measurement device and a control device. The distribution system according to the third embodiment is the same type as that shown in FIG. Here, it demonstrates centering on the difference from before.

  FIG. 12 shows a configuration of a distribution system 100 according to the third embodiment of the present invention. The communication device 18 includes a measurement device 40 and a control device 42, and the wireless device 10 does not include them. The measuring device 40 in the communication device 18 derives the time difference as before. The control device 42 determines a network based on the derived time difference. The communication device 18 transmits the determined network to the wireless device 10. Here, the determined network may be stored in the measurement response packet, or may be stored in a different packet.

  According to the embodiment of the present invention, since the delay difference is derived in the communication device and the network is determined, the processing amount of the wireless device can be reduced. In addition, since the measurement device and the control device are arranged in the communication device, the degree of design freedom can be improved.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the encoder 30 inputs moving image data from an imaging device (not shown). However, the present invention is not limited thereto. For example, the encoder 30 inputs audio data together with moving image data from an imaging device (not shown), and the distribution system 100 performs processing similar to the processing performed on moving image data described in the embodiments. May be performed on the audio data.

  In the embodiment of the present invention, the transmitting device corresponds to the wireless device 10, and the receiving device corresponds to the communication device 18. However, the present invention is not limited to this. For example, the transmission device may correspond to a wired communication system, and the reception device may correspond to a wireless communication system. In addition, both the transmission device and the reception device may correspond to a wireless communication system or a wired communication system. According to this modification, the degree of freedom in designing the distribution system 100 can be improved.

  In the embodiment of the present invention, the wireless device 10 and the communication device 18 each include two communication units 36. However, the present invention is not limited to this. For example, the wireless device 10 and the communication device 18 may include three or more communication units 36. Further, the communication unit 36 provided in each of the wireless device 10 and the communication device 18 may be different. Further, one of the wireless device 10 and the communication device 18 may include one communication unit 36. According to this modification, the degree of freedom in designing the distribution system 100 can be improved.

  DESCRIPTION OF SYMBOLS 10 Radio | wireless apparatus, 12 Base station apparatus, 14 Network, 16 Internet, 18 Communication apparatus, 30 Encoder, 32 Streaming protocol control part, 34 Transmission control part, 36 Communication part, 38 Measurement control part, 40 Measurement apparatus, 42 Control apparatus , 44 derivation unit, 46 determination unit, 60 reception control unit, 62 streaming protocol control unit, 64 streaming buffer, 66 decoder, 68 measurement control unit, 100 distribution system.

Claims (4)

A first acquisition unit that acquires a first time at which the transmission device transmits a first signal to the reception device via the first network;
A second acquisition unit that acquires a second time at which the reception device receives the first signal;
A third acquisition unit for acquiring a third time at which the transmission device transmits a second signal to the reception device via a second network;
A fourth acquisition unit for acquiring a fourth time at which the reception device receives the second signal;
Based on the first time acquired by the first acquisition unit, the second time acquired by the second acquisition unit, the third time acquired by the third acquisition unit, and the fourth time acquired by the fourth acquisition unit. A derivation unit for deriving a relative transmission delay difference between the first network and the second network;
With
The first time and the third time are timed with a clock in the transmitting device, and the second time and the fourth time are timed with a clock in the receiving device. A measuring device. (1) a first time at which the transmission device transmits a first signal to the reception device via the first network, (2) a second time at which the reception device receives the first signal, and (3) the transmission device. A third time when the second signal is transmitted to the receiving device via the second network; and (4) a transmission delay difference derived based on a fourth time when the receiving device receives the second signal. And an acquisition unit for acquiring a relative transmission delay difference between the first network and the second network;
A determination unit that determines the first network or the second network as a path when the transmission device transmits a signal to the reception device based on the transmission delay difference acquired by the acquisition unit;
With
The first time and the third time are timed with a clock in the transmitting device, and the second time and the fourth time are timed with a clock in the receiving device. Control device. Obtaining a first time at which the transmitting device has transmitted the first signal to the receiving device via the first network;
Obtaining a second time at which the receiving device receives the first signal;
Obtaining a third time at which the transmitting device transmits a second signal to the receiving device via a second network;
Obtaining a fourth time at which the receiving device receives the second signal;
A relative transmission delay difference between the first network and the second network is derived based on the acquired first time, acquired second time, acquired third time, and acquired fourth time. And steps to
With
The first time and the third time are timed with a clock in the transmitting device, and the second time and the fourth time are timed with a clock in the receiving device. Measurement method. (1) a first time at which the transmission device transmits a first signal to the reception device via the first network, (2) a second time at which the reception device receives the first signal, and (3) the transmission device. A third time when the second signal is transmitted to the receiving device via the second network; and (4) a transmission delay difference derived based on a fourth time when the receiving device receives the second signal. And obtaining a relative transmission delay difference between the first network and the second network;
Determining the first network or the second network as a path when the transmitting device transmits a signal to the receiving device based on the acquired transmission delay difference;
With
The first time and the third time are timed with a clock in the transmitting device, and the second time and the fourth time are timed with a clock in the receiving device. Control method.

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