JP2006333309A - Data communications system and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data communications system and its method, in which packet losses can be reduced when implementing data delivery service by multicast communication on a wireless LAN. <P>SOLUTION: There is provided a data communications system including a network for transmitting information data based on a multicast communication method, a wireless router that is connected with a network to relay the information data, at least one wireless terminal for receiving the information data relayed by the wireless router, and at least one user apparatus for receiving the information data from the wireless terminal. The data communications system is provided with a first communication means for transmitting the information data received in the wireless router by the multicast communication method to the wireless terminal based on a unicast communication method and a second communication means for supplying the information data received from the wireless router in the wireless terminal by the unicast communication method to the user apparatus based on the multicast communication method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data communication system and a data communication method used in a wireless LAN for relaying a content distribution service such as video and audio from a network.

  In recent years, services that distribute content such as video, audio, and music to users via networks such as the Internet are rapidly spreading. Typical examples of these services include, for example, a video on demand (hereinafter simply referred to as “VOD”) service in which content such as video and audio is delivered to users in a one-to-one format. There is a so-called IP broadcast service in which a service provider distributes program contents such as CS broadcast or BS broadcast to users in a one-to-n broadcast format.

  By the way, there are mainly two methods for transmitting data such as video and audio by IP (Internet Protocol) packets on the Internet. One is unicast communication that transmits data using unicast packets, and the other is multicast communication that transmits data using multicast packets. It is. Unicast communication mainly consists of communication addressed to one node using a single destination address, so that the service provider and the user are connected in a one-to-one relationship. For example, the user selects It is suitable for a VOD service that performs real-time processing such as fast-forwarding and pausing images while viewing content. Multicast communication, on the other hand, can broadcast a large amount of data by simple frame exchange, and is suitable for the above IP broadcasting service because the bandwidth that occupies the network is narrow even if large-scale data distribution is performed. Yes.

  On the other hand, users who receive such services via a network such as the Internet also have a wireless connection between the wireless router connected to the network and each terminal device as the performance of the terminal device increases and the price decreases. Increasing cases of connecting so-called wireless LAN systems are also increasing. In such a wireless LAN system on the user side, for example, a low-power radio wave or a weak radio wave compliant with, for example, the IEEE 802 standard or the Bluetooth standard is often used as a radio medium. Therefore, due to the vulnerabilities peculiar to the wireless media used, these wireless LAN systems transmit on the wireless LAN due to the influence of the location of wireless terminals, the surrounding radio wave propagation environment, or the radio noise generated by other home appliances. Data packets may be missing.

  In the above-described unicast communication, a communication control procedure is adopted in which the receiving side notifies the transmitting side of data reception completion with an ACK signal, and data is retransmitted from the transmitting side when data loss occurs due to a transmission error. ing. Therefore, in unicast communication, even when packet loss occurs on the wireless LAN, the transmission quality of data is maintained based on a predetermined standard.

  On the other hand, in the above-described multicast communication, since it is necessary to broadcast a large amount of data all at once, it is not possible to perform confirmation of received data using such an ACK signal and data retransmission processing when data is lost. Therefore, in the case of multicast communication, if packet loss occurs on the wireless LAN, the transmission quality of the data is remarkably deteriorated and content such as video / audio received on the user side is disturbed.

In order to solve such a problem, for example, a conventional technique as disclosed in Patent Document 1 is disclosed. This document uses unicast communication until the establishment of a communication link whose transmission path is unstable in data transmission between terminals, and once the communication link is established, a large amount of data is transmitted using multicast communication. The invention is shown. Such a conventional technology can reduce data traffic and improve the reliability of data transmission under a so-called peer-to-peer network configuration without using a server. However, because unicast communication and multicast communication are used alternately in a time-sharing manner, they are familiar with data transmission systems such as IP broadcast services that download content from service providers simultaneously via a network server. There is no problem.
JP 2003-283559 A

  The present invention has been made to solve such problems, and in particular, a data communication system capable of reducing packet loss when a data distribution service by multicast communication is performed on a wireless LAN. And a data communication method.

  The present invention provides a network that transmits information data based on a multicast communication scheme, a wireless router that is connected to the network and relays the information data, and at least one wireless that receives the information data relayed by the wireless router A data communication system including a terminal and at least one user equipment that receives information data from the wireless terminal, wherein the wireless router receives the information data received in a multicast communication scheme based on a unicast communication scheme 1st communication means to transmit toward the said radio | wireless terminal, The said radio | wireless terminal supplies the said information data received by the unicast communication system from the said wireless router toward the said user apparatus based on a multicast communication system The second communication means is included.

  The present invention also provides a network that transmits information data based on a multicast communication scheme, a wireless router that is connected to the network and relays the information data, and at least one that receives the information data relayed by the wireless router. A data communication method in a system including two wireless terminals and at least one user equipment that receives information data from the wireless terminal, wherein the wireless router performs unicast communication on the information data received by a multicast communication method. Including a processing step of transmitting to the wireless terminal based on a method, wherein the wireless terminal transmits the information data received from the wireless router by a unicast communication method to the user equipment based on a multicast communication method. Including a supplying process step.

  FIG. 1 is a configuration diagram showing an outline of a data communication system according to an embodiment of the present invention.

  In FIG. 1, an IP network 10 is an information network such as the Internet that transmits data such as video, audio, and music by IP packets. The service provider 70 is connected to the IP network 10 via a predetermined node, and is a communication device such as a server that provides a broadcast type broadcast service such as an IP broadcast service or Internet radio to a large number of users by multicast communication. It is.

  The user-side wireless LAN 20 is a LAN system that uses a wireless communication medium set in the premises of a user who receives a service from the above provider via the IP network 10. The user-side wireless LAN 20 is mainly composed of a wireless router 30, a client terminal (hereinafter referred to as “CT terminal”) 40, a personal computer terminal (hereinafter referred to as “PC terminal”) 60, and data from the CT terminal in a user's home such as a television. And a set top box (STB) 50 having a server function, a data function, and the like to be supplied to the audio-visual equipment.

  The wireless router 30 is connected to the IP network 10 via an ADSL service of a subscriber telephone line, an FTTH service using an optical fiber line, or the like. The wireless router 30 is connected to the CT terminal 40 and the PC terminal 60 by, for example, a wireless LAN system that uses a low-power radio wave such as IEEE 802.11 standard as a communication medium.

  The PC terminal 60 is used when receiving a content service provided by a provider on a personal computer, and the CT terminal 40 is a content service provided by a user audiovisual device such as a television or a large screen display via the STB 50. It is a form of use when receiving the provision of. Since these usage modes are not particularly different in the description of the present embodiment, in the following description, the CT terminal 40 and the PC terminal 60 are collectively referred to as “wireless terminal 40”, and the STB 50 is related. Are referred to as “user equipment 50” including user audiovisual equipment such as a television connected thereto.

  Next, the operation of the present embodiment will be described based on the system configuration diagram of the user-side wireless LAN 20 shown in FIG.

  First, in this embodiment, it is assumed that the service provider 70 performs an IP broadcast type service under a communication control procedure using multicast communication. In other words, content data relating to video, audio, music, etc. from the service provider 70 is distributed to the wireless router 30 of the user-side wireless LAN 20 via the IP network 10 by multicast packets. Data transmission between the service provider 70 and the wireless router 30 is performed by multicast communication that does not use the reception confirmation by the ACK signal, and the transmission quality in the transmission section satisfies a predetermined transmission quality standard regarding the network or the like. Therefore, there is no possibility that a packet loss that causes a problem in the transmission process occurs.

  On the other hand, as shown in FIG. 2, a first communication module 31 is provided inside the wireless router 30. The module transmits a multicast packet received from the IP network 10 by a unicast communication method. The wireless router 30 performs predetermined modulation processing on the carrier wave with data based on the unicast packet, and then performs processing such as frequency conversion to transmit radio waves to the wireless section of the LAN.

  As described above, in unicast communication using unicast packets, every time the transmitting side transmits a fragment that is a predetermined data packet group, the receiving side notifies the transmitting side of the completion of reception of the fragment by an ACK signal. However, data transmission is performed. On the other hand, in multicast communication, data transmission is performed by a simple frame exchange process without fragmenting a data packet and without performing reception confirmation using an ACK signal. Therefore, when the communication control procedure is converted from unicast communication to multicast communication, there is a possibility that a gap may occur in the speed of data transmission between the two communication methods.

  Various methods are conceivable as a method for solving such a problem. For example, a buffer memory is provided in the first communication module 31, data related to multicast packets is temporarily stored in the memory, and the communication control procedure using unicast packets is executed by sequentially using the accumulated data. Also good. Alternatively, using a FIFO (First in First Out) memory, the data in the multicast packet is used as the FIFO input, the data in the unicast packet is used as the FIFO output, and the communication speed between the FIFO inputs and outputs is adjusted. You may make it change.

  The unicast packet transmitted from the wireless router 30 to the wireless terminal 40 via the wireless section of the user-side wireless LAN 20 is restored to the original multicast packet in the second communication module 41 provided in the terminal. Is done. In addition, the 2nd communication module 41 shall convert a communication control procedure with the method contrary to said 1st communication module 31. FIG. The data restored to the multicast packet by the second communication module 41 is supplied to the user equipment 50 connected to the wireless terminal 40 by a communication control procedure by multicast communication.

  Next, the operation of the processing sequence according to the present embodiment will be described based on the sequence chart of FIG.

  First, when the user-side wireless LAN 20 is started up, for example, by turning on each system device or inputting a reset signal, an initial setting command signal is sent from the predetermined user-side device that controls the entire LAN system to the wireless terminal 40. Via the wireless router 30. In response to the initial setting command signal, the wireless router 30 sets up a function of converting the multicast packet of the first communication module 31 into a unicast packet (step S01). Needless to say, a function for converting the unicast packet of the second communication module 41 into a multicast packet is set up in the wireless terminal 40 in response to the initial setting command signal.

  When the initial setting process is completed, a multicast communication start process is subsequently executed. First, a request signal for requesting to join a specific multicast group is notified to the wireless router 30 via a wireless LAN from a predetermined user side device that controls the above control. The wireless router 30 transmits the signal to the service provider router via the IP network 10 (step S02). When the service provider receives such a request signal, the service provider checks the suitability of the service supply to the user, and if the service provider recognizes that the user is a proper user, the permission command signal permits the joining to a specific multicast group. Is returned via the IP network 10 (step S03). Thus, the multicast communication start process is completed, and thereafter, the data content communication process from the service provider is started.

  Along with the start of the communication process, various contents such as video, audio and music are transmitted from the service provider to the wireless router 30 via the IP network 10 by multicast packets (step S04). Upon receiving the distribution of the content data, the wireless router 30 drives the first communication module 31 to convert the received multicast packet data into a unicast packet (step S05), and converts the converted data into a unicast packet. It transmits to the radio | wireless terminal 40 by cast communication (step S06). In other words, even if a packet loss occurs in the wireless section where the transmission error is most likely to occur, data transmission is performed by unicast communication that confirms reception using an ACK signal, so that deterioration in transmission quality due to packet loss can be reduced. .

  On the other hand, on the wireless terminal 40 side, the unicast data pad received from the wireless router 30 is converted again into a multicast packet in the second communication module (step S07), and the converted data is multicast. It transmits to the user side apparatus 50 by communication (step S08). In other words, the user equipment 50 can be used without any modification or change to software corresponding to normal multicast communication.

  When the download of service content from the service provider to the user is completed, a request signal for requesting separation from a specific multicast group is sent via a wireless LAN from a predetermined user side device that controls the entire LAN system. The wireless router 30 is notified. Then, the wireless router 30 transmits the same signal to the service provider router via the IP network 10 (step S09), and ends the process.

As described above, in this embodiment, the content data is finally supplied to the user equipment in the form of a multicast packet. Therefore, it is possible to handle the user-side device in the same manner as in the past, and it is not necessary to modify the software for driving the user-side device. In addition, since data transmission in the wireless section of the wireless LAN is made unicast communication, even if packet loss occurs under unstable radio wave propagation conditions, transmission quality is ensured by data retransmission processing by ACK control. . That is, according to the present embodiment, it is possible to provide a higher quality service than the data content distribution service by the conventional multicast communication without any change to the user side device.

FIG. 1 is a configuration diagram showing an outline of a data communication system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of the user-side wireless LAN 20 in the data communication system of FIG. FIG. 3 is a sequence chart showing the flow of processing in the data communication system of FIG.

Explanation of symbols

10 IP network 20 User side wireless LAN
30 wireless router 31 first communication module 40 client terminal (wireless terminal)
41 Second communication module 50 Set-up box (user equipment)
60 PC terminal 70 Service provider

Claims (2)

A network that transmits information data based on a multicast communication scheme, a wireless router that is connected to the network and relays the information data, at least one wireless terminal that receives the information data relayed by the wireless router, and A data communication system comprising: at least one user equipment that receives information data from a wireless terminal;
The wireless router includes first communication means for transmitting the information data received by a multicast communication method to the wireless terminal based on a unicast communication method,
The data communication system, wherein the wireless terminal includes second communication means for supplying the information data received from the wireless router by a unicast communication method to the user equipment based on a multicast communication method. A network that transmits information data based on a multicast communication scheme, a wireless router that is connected to the network and relays the information data, at least one wireless terminal that receives the information data relayed by the wireless router, and A data communication method in a system including at least one user equipment that receives information data from a wireless terminal,
The wireless router includes a processing step of transmitting the information data received by a multicast communication method to the wireless terminal based on a unicast communication method,
The data communication method comprising: a processing step in which the wireless terminal supplies the information data received from the wireless router by a unicast communication method to the user equipment based on a multicast communication method.

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