JP4408743B2 - Communication apparatus and reception buffer control method - Google Patents

Description

  The present invention relates to a real-time communication apparatus, and more particularly to a reception buffer memory capacity control method for improving communication quality by absorbing delay fluctuation of a data packet and a real-time communication apparatus including the same.

  When data that requires real-time performance such as voice and moving images is transmitted and received as IP packets on an IP (Internet Protocol) network, the delay occurs due to variations in delay time caused by passing through the IP network. The arrival interval of the received data fluctuates (hereinafter referred to as delay fluctuation), and the sound quality of the received voice is interrupted, the image is disturbed, and the communication quality is lowered. For this reason, a real-time communication device that transmits and receives data that requires real-time performance such as voice and moving images over an IP network is provided with a reception buffer that temporarily stores received data in order to absorb delay fluctuations. The communication quality is improved.

  The larger the storage capacity of the reception buffer, the more the interruption of audio / video can be prevented due to delay fluctuations. On the other hand, if the storage capacity of the buffer memory is increased, the playback of received data (sound playback, video display) Etc.) There is a disadvantage that it leads to delay and the real-time property is lowered. For this reason, it is necessary to set the storage capacity of the reception buffer memory so that the delay time can be effectively absorbed while the delay time is not increased excessively. Furthermore, since the congestion status of the IP network that causes delay fluctuations in received data changes, it is desirable that the capacity of the reception buffer memory can be changed in accordance with this change.

In Patent Document 1, a call device used in a data communication network such as the Internet network is obtained by counting the number of packets and the packet length of packets that travel within a predetermined time on a network segment to which the call device is directly connected. A technique for increasing or decreasing the number of FIFO stages of the reception buffer memory included in the communication device based on the obtained value is disclosed.
JP 2002-152257 A

  However, in the conventional technique disclosed in Patent Document 1, since the traffic congestion status of the data communication network is determined using the number of packets and the packet length that travel on the network segment to which the telephone device is directly connected, It is impossible to capture the traffic congestion status of the entire data communication network other than the network segment to which the communication device is directly connected. For this reason, when delay fluctuation occurs due to the complexity of the network configuration of the data communication network other than the network segment directly connected to the communication device, the number of FIFO stages corresponding to the storage capacity of the reception buffer memory can be optimized. Therefore, there is a problem that the call quality is degraded.

  The present invention has been made to solve the above-described problems, and absorbs delay fluctuations in received data packets by increasing or decreasing the storage capacity of the reception buffer of the real-time communication device according to the complexity of the configuration of the data communication network. An object of the present invention is to provide a real-time communication apparatus and a reception buffer control method.

  A real-time communication apparatus according to the present invention receives a data packet from a communication network, extracts a communication data contained in the received data packet, a means for temporarily storing the communication data in a reception buffer, and a storage in the reception buffer Means for transmitting the communication data to the reproduction means, wherein the data packet includes means for obtaining information on the number of relay devices through which the data packet has passed from a header of the data packet; And a means for changing the storage capacity of the reception buffer based on the information on the number of relay devices passed. With such a configuration, the capacity of the reception buffer can be changed based on the number of relay devices through which the data packet has passed, so by increasing or decreasing the storage capacity of the reception buffer of the real-time communication device according to the complexity of the configuration of the data communication network The delay fluctuation of the received data packet can be absorbed.

  On the other hand, a reception buffer control method according to the present invention includes a means for receiving a data packet from a communication network, extracting communication data contained in the received data packet, means for temporarily storing the communication data in a reception buffer, A method for controlling the reception buffer in a real-time communication apparatus having means for transmitting the communication data stored in the reception buffer to a reproducing means, wherein the number of relay apparatuses through which the data packet passes from the header information of the data packet And a step of changing the storage capacity of the reception buffer based on information on the number of relay devices through which the data packet has passed. By such a control method, the capacity of the reception buffer can be changed based on the number of relay devices through which the data packet has passed, so the storage capacity of the reception buffer of the real-time communication device can be increased or decreased according to the complexity of the configuration of the data communication network. Thus, the delay fluctuation of the received data packet can be absorbed.

  Further, the reception buffer capacity is changed by increasing the storage capacity of the reception buffer as the number of relay apparatuses indicated by the information on the number of relay apparatuses through which the data packet has passed increases. It is desirable to control so that the storage capacity of the reception buffer decreases as the number of relay devices indicated by the information on the number of relay devices decreases. With such a configuration, it is possible to efficiently absorb the delay fluctuation of the received data packet caused by the complexity of the configuration of the data communication network, so that the communication quality can be improved.

  When the data packet is an IP packet, the information regarding the number of relay devices through which the data packet has passed may be the TTL value included in the IP header, and as the TTL value decreases, the reception buffer accumulates. The capacity may be increased, and conversely, the storage capacity of the reception buffer may be controlled to decrease as the TTL value increases.

  According to the present invention, there is provided a real-time communication device and a reception buffer control method that absorbs delay fluctuation of a received data packet by increasing / decreasing the storage capacity of the reception buffer of the real-time communication device according to the complexity of the configuration of the data communication network. Can do.

Embodiment 1 of the Invention
FIG. 1 is a block diagram showing a configuration of a real-time communication apparatus 1 according to the present embodiment. The real-time communication device 1 is a voice call device for making a voice call on an IP network. The real-time communication device 1 includes a transmission unit 10 and a reception unit 20. Among these, the transmission part 10 is a function part for transmitting the encoded audio | voice signal to the other party's real-time communication apparatus via an IP network. In the transmission unit 10, first, an audio signal input from the microphone 11 is sent to the encoding processing unit 12. The encoding processing unit 12 converts the audio signal received from the microphone 11 into digital compression data by a standard encoding method such as a PCM (Pulse Code Modulation) method or a CS-ACELP method, and converts the converted digital compressed data into a header. It transmits to the addition part 13. The header adding unit 13 adds header information necessary for communication including at least an IP header to the digital compressed data received from the encoding processing unit 12 to assemble an IP packet. The header adding unit 13 may divide the digital compressed data into IP packet sizes and assemble IP packets as necessary. Further, the header addition unit 13 transmits the assembled IP packet to the packet transmission unit 14. The packet transmission unit 14 transmits the IP packet received from the header addition unit 13 to the counterpart terminal device according to the communication method of the IP network 2.

  On the other hand, the receiving unit 20 is a functional unit that receives data obtained by compressing and encoding an audio signal from a real-time communication device that is a transmission source, decodes the received data into an audio signal, and reproduces it. In the receiving unit 20, first, the packet receiving unit 21 receives an IP packet sent from the counterpart real-time communication device via the IP network 2, and the received IP packet is converted into a TTL value detecting unit 22 and a header removing unit. 23. Among these, the header removal unit 23 removes the header information including the IP header from the IP packet received from the packet reception unit 21 to extract the digital compressed data, and outputs the extracted digital compressed data to the reception buffer unit 24 according to the reproduction order. To do. The reception buffer unit 24 temporarily stores the digital compressed data input from the header removal unit 23. Further, the reception buffer unit 24 sequentially transmits the stored digital compressed data to the decoding processing unit 25. The decode processing unit 25 decodes the digital compressed data received from the reception buffer unit 24 into an original audio signal, and outputs it to the speaker 26. The speaker 26 reproduces the audio signal output from the decoding processing unit 25.

  The reception buffer unit 24 is a memory having a FIFO structure, and is configured so that the number of FIFO stages used for storing digital compressed data can be changed by an instruction of the TTL value detection unit 22.

  Next, the operation of the TTL value detection unit 22 will be described. The TTL value detection unit 22 detects a TTL (Time To Live) value included in the header of the IP packet received from the packet reception unit 21, and stores the storage capacity (hereinafter, reception buffer capacity) of the reception buffer unit 24 according to the TTL value. ) Is output to the reception buffer unit 24 (hereinafter, referred to as a reception buffer control signal). The reception buffer capacity is determined based on the reception buffer control signal output from the TTL value detection unit 22.

  FIG. 2 is a graph conceptually showing the relationship between the TTL value indicated by the reception buffer control signal output from the TTL value detection unit 22 and the reception buffer capacity. As shown in the figure, when the TTL value included in the IP header of the received IP packet is large, a reception buffer control signal instructing to relatively reduce the reception buffer capacity is sent from the TTL value detection unit 22 to the reception buffer unit 24. When the TTL value is output, a reception buffer control signal that instructs to increase the reception buffer capacity is output.

  As described above, the present invention is characterized in that the capacity of the reception buffer is changed according to the TTL value of the received IP packet using the TTL value mounted in the IP header. Hereinafter, advantages of increasing / decreasing the reception buffer capacity based on the TTL value will be described.

  The TTL value is a value representing the valid period of the IP packet defined in the 8-bit area in the IP header, and is represented by an integer value from 0 to 255 by displaying in decimal. When the source terminal device sets a TTL value and transmits an IP packet toward the destination terminal device, the value is decreased by 1 by the router device every time it passes through the router device on the way. If the IP packet does not reach the communication destination terminal device before the value becomes 0, the IP packet is discarded by the router device at that time. That is, the TTL value represents the validity period of the IP packet by the number of hops that is the number of times the router device passes. For this reason, by detecting the TTL value of the IP packet received by the terminal device 1, it is possible to know the number of router devices existing on the path to the transmission source real-time communication device.

  The increase in the number of router devices through which IP packets pass before reaching the destination real-time communication device increases the arrival delay time of IP packets that should reach the destination real-time communication device continuously, and delay fluctuations. Causes an increase. Therefore, a small TTL value of the received IP packet corresponds to a large number of hops, and it is assumed that the delay fluctuation of the IP packet is large. In this case, the reception buffer capacity is set to be relatively large. Control the buffer. Conversely, since a large TTL value corresponds to a small number of hops, the reception buffer capacity is controlled to be relatively small. As a result, it is possible to efficiently control the reception buffer capacity in accordance with the delay fluctuation of the IP packet caused by the IP network through which it passes.

  FIG. 3 shows an example of a configuration in which the real-time communication device 1 according to the present embodiment communicates via an IP network. In the example of FIG. 3, a first real-time communication device 1 </ b> A and a second real-time communication device 1 </ b> B that are real-time communication devices according to the present embodiment are connected to the IP network 2. Further, in the IP network 2, four router devices 30 to 33 are arranged on a route through which the real-time communication devices 1A and 1B communicate. The first real-time communication device 1A and the router device 30 are connected, and further the router device 30 and the router device 31, the router device 31 and the router device 32, the router device 32 and the router device 33, and finally the router device 33 and the second communication. Terminals 1B are connected to each other.

  A case where an IP packet is transmitted from the first real-time communication apparatus 1A to the second real-time communication apparatus 1B will be described as an example. The TTL value of the IP packet to be transmitted is given by the first real-time communication apparatus 1A that is the transmission source, and is 128 in the example of FIG. When the IP packet transmitted from the transmission unit 10 of the first real-time communication device 1A passes through the first router device 30, the TTL value is subtracted to 127. Subsequently, also in the router devices 31 to 33, the TTL value is similarly subtracted, and the TTL value when the IP packet reaches the receiving unit 20 of the second real-time communication device 1B as the communication destination becomes 124.

  On the other hand, the simplest configuration is considered for comparison. The simplest configuration is that there is no router device on the route between the first real-time communication device 1A and the second real-time communication device 1B in the IP network 2, and it passes through the router device on the way. This is a case where communication is possible. In this case, the IP packet transmitted as the TTL value 128 from the real-time communication device 1A is received as the TTL value 128 by the real-time communication device 1B.

  FIG. 4 is a graph showing an example of a change in the reception buffer capacity corresponding to the configuration of FIG. In the case of the configuration described with reference to FIG. 3, since the TTL value of the IP packet received by the receiving unit 20 of the real-time communication apparatus 1B is 124, the reception buffer capacity at this time is A, and the TTL value detecting unit 22 A reception buffer control signal having a reception buffer capacity A is output to the reception buffer unit 24. On the other hand, the TTL value of the IP packet received by the receiving unit 20 of the real-time communication device 1B without going through the router device is 128. At this time, the TTL value detecting unit 22 receives the reception buffer with the reception buffer capacity set to the minimum value Min. The control signal is output to the reception buffer unit 24. As shown in FIG. 4, the relationship of A> Min is satisfied, and reception is instructed to increase the reception buffer capacity of the reception buffer unit 24 in the case of the configuration described in FIG. A buffer control signal is output.

  Next, a control flow of storage capacity control of the reception buffer unit 23 performed by the TTL value detection unit 22 will be described with reference to FIG. First, in step S1, an IP packet is fetched from the packet receiver 21, and a TTL value is acquired from the header. Next, the TTL value acquired in step S2 is compared with the TTL value held as the previous value (current value). If there is no change in the TTL value as a result of the comparison, the next IP packet is captured. On the other hand, when there is a change in the TTL value, the reception buffer capacity corresponding to the new TTL value is determined (step S3), and a reception buffer control signal that instructs the reception buffer unit 24 to change the storage capacity is transmitted. (Step S4). In addition, what is necessary is just to comprise so that the TTL value detection part 22 may hold | maintain the relationship between the received TTL value and reception buffer capacity which are required in order to determine reception buffer capacity.

  As described above, the delay fluctuation of the network packet generated in the IP network 2 can be absorbed by controlling the reception buffer capacity to increase when the TTL value of the reception IP packet is small. In addition, when the TTL value is large, the increase in the delay time caused by the reception buffer unit 24 can be suppressed by controlling the reception buffer capacity to be small. As described above, in the real-time communication apparatus 1 according to the present embodiment, the delay fluctuation can be efficiently absorbed by appropriately changing the reception buffer capacity based on the TTL value, so that the communication quality is improved by eliminating the interruption of the received voice. Can be made.

Embodiment 2 of the Invention
FIG. 6 is a block diagram showing a configuration of the real-time communication apparatus 3 according to the present embodiment. The real-time communication device 3 includes a video camera 40 instead of the microphone 11 and a display 41 instead of the speaker 26 in the real-time communication device 1 according to the first embodiment of the invention described with reference to FIG. . The encoding processing unit 12 included in the real-time communication device 3 performs compression encoding of a moving image, and the decoding processing unit 25 performs operations and actions other than the point of performing decoding decoding of the moving image, as in the first embodiment of the invention. It is. As a result, the real-time communication apparatus 3 according to the present embodiment can improve the communication quality by eliminating the interruption of the moving image displayed on the display 41 on the receiving side.

Embodiment 3 of the Invention
FIG. 7 is a block diagram showing a configuration of the real-time communication apparatus 4 according to the present embodiment. The real-time communication device 4 includes a first real-time data application 42 such as an electronic blackboard instead of the microphone 11 in the real-time communication device 1 according to the first embodiment of the invention described with reference to FIG. A second real-time data application 43 is provided. In general, when dealing with a real-time data application, the encoding processing unit 12 is not provided because it is not necessary to compress and encode the transmission data, and similarly, the decoding processing unit does not need to perform decompression decoding of the received data. 25 is not provided. Other operations and functions are the same as those of the first embodiment. As a result, in the real-time communication device 4 according to the present embodiment, it is possible to improve the communication quality without interruption of data processed by the real-time data application 43 on the receiving side.

Embodiment 4 of the Invention
FIG. 8 is a block diagram showing a configuration of the real-time communication apparatus 5 according to the present embodiment. The real-time communication device 5 is a receiving terminal used when transmitting a moving image in one direction, and receives the moving image transmitted from the transmitting terminal 6 via the IP network 2. The real-time communication device 5 has a functional unit corresponding to the receiving unit 20 of the real-time communication device 3 according to the second embodiment of the invention, and the decoding processing unit 25 operates other than the point that performs decompression decoding of moving images. The operation is the same as that of the receiving unit of the real-time communication apparatus 1 according to the first embodiment of the invention.

  The above-described configuration according to the embodiment of the present invention is an example, and a data packet that requires real-time property is transmitted / received via a communication network, and a delay fluctuation of the received data packet is performed using a reception buffer memory. The present invention is also effective in other real-time communication devices that absorb light.

  For example, in the above-described embodiment of the present invention, the case where the TTL value included in the IPv4 header is used as the information related to the number of relay devices through which the data packet passes is described. However, in the case of a real-time communication device that performs data communication according to the IPv6 protocol. If the reception buffer capacity is changed based on the value of the hop limit field included in the IPv6 header, the same effect as that of the real-time communication apparatus according to the above-described embodiment can be achieved.

It is a functional block diagram which shows the structure of the real-time communication apparatus concerning Embodiment 1 of invention. It is a graph which shows the relationship between a TTL value and receiving buffer capacity. It is a figure which shows an example of the structure which the real-time communication apparatus concerning Embodiment 1 communicates. It is a graph which shows the relationship between a TTL value and receiving buffer capacity. It is a control flowchart of reception buffer capacity control. It is a functional block diagram which shows the structure of the real-time communication apparatus concerning Embodiment 2 of invention. It is a functional block diagram which shows the structure of the real-time communication apparatus concerning Embodiment 3 of invention. It is a functional block diagram which shows the structure of the real-time communication apparatus concerning Embodiment 4 of invention.

Explanation of symbols

1, 3, 4, 5 Real-time communication device, 2 IP network, 22 TTL value detection unit, 23 header removal unit, 24 reception buffer unit, 25 decoding unit, 26 speaker

Claims (7)

A reception buffer for temporarily storing communication data acquired from each of a plurality of data packets sequentially received prior to reproduction processing;
Each data packet acquired from the header of each of the plurality of data packets passes through continuously after the reproduction process of the communication data to be reproduced first among the communication data stored in the reception buffer is started. The information indicating the number of relay devices that have been acquired is sequentially referred to and newly acquired when the number of relay devices indicated by the newly acquired information has changed from the number of relay devices indicated by the previously acquired information. Updating means for sequentially updating the storage capacity of the reception buffer so as to have a size corresponding to the number of relay devices indicated by the information,
A communication device comprising: The updating means includes
When the number of relay apparatuses indicated by the newly acquired information increases from the number of relay apparatuses indicated by the information acquired immediately before, the storage capacity is increased according to the increase amount,
The storage capacity is reduced according to the amount of decrease when the number of relay apparatuses indicated by the newly acquired information decreases from the number of relay apparatuses indicated by the information acquired immediately before. The communication apparatus according to 1. Each of the plurality of data packets is an IP packet, and information regarding the number of relay devices through which the data packet has passed is a TTL value included in the IP header,
The update means increases the storage capacity of the reception buffer according to a decrease in the TTL value, and decreases the storage capacity of the reception buffer according to an increase in the TTL value.
The communication apparatus according to claim 1.   When the number of relay apparatuses indicated by the newly acquired information has changed from the number of relay apparatuses indicated by the information acquired immediately before, the updating unit is configured to store the storage capacity according to the change. The communication device according to claim 1, wherein the communication device is updated. A method of controlling a reception buffer in a communication device for temporarily storing communication data acquired from each of a plurality of data packets sequentially received in a reception buffer prior to reproduction processing ,
Each data packet acquired from the header of each of the plurality of data packets passes through continuously after the reproduction processing of communication data to be reproduced first among the communication data stored in the reception buffer is started. The information indicating the number of relayed devices is sequentially referred to, and newly acquired when the number of relay devices indicated by the newly acquired information has changed from the number of relay devices indicated by the previously acquired information. A receiving buffer control method including an updating step of sequentially updating a storage capacity of the receiving buffer so as to have a size corresponding to the number of relay apparatuses indicated by the information . In the updating step,
When the number of relay apparatuses indicated by the newly acquired information increases from the number of relay apparatuses indicated by the information acquired immediately before, the storage capacity is increased according to the increase amount,
When the number of relay devices indicated by the newly acquired information is decreased from the number of relay devices indicated by the information acquired immediately before, the storage capacity is reduced according to the amount of decrease.
The method for controlling a reception buffer according to claim 5.   In the updating step, when the number of relay apparatuses indicated by the newly acquired information has changed from the number of relay apparatuses indicated by the information acquired immediately before, the storage capacity is changed according to the change. The receiving buffer control method according to claim 5, wherein:

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