JP2011114485A - Radio repeater and data communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely transfer data of sound, a moving picture or the like, transmitted by multicast communication without deteriorating a data quality. <P>SOLUTION: This radio repeater 1 which transfers multicast communication data received from a network 2 to a terminal 3 through a radio transmission path is equipped with: a line control part 4 for receiving a multicast packet to a multicast group from the network 2; a storing part 5 for storing an address table in which the address of a terminal participating in the multicast group is set; a packet converting part 6 for converting the multicast packet received by the line control part 4 into a unicast packet by referring to the address table stored in the storing part 5; and a radio control part 7 for transmitting and receiving a packet by radio communication to/from the terminal 3, wherein the radio control part 7 transfers communication data converted into the unicast packet by the packet converting part 6 to the terminal 3 at a transfer speed equal to or higher than a predetermined minimum transfer rate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless relay device and a data communication method for transferring data such as voice and moving images transmitted by a multicast packet via a wireless transmission path.

  When multicast communication is used for delivery of audio, video, etc., the transport layer uses RTP / UDP (Real-time Transport Protocol / User Datagram Protocol), and the IP layer uses IP multicast. . When IP multicast is used in a wireless LAN, wireless LAN multicast transfer is used.

  However, since the multicast transfer of the wireless LAN does not have a retransmission function, when packet loss occurs, information on the lost packet is lost. In addition, when sending multicast packets using a wireless LAN, in order to ensure transmission to all terminals, data is transmitted and received using a low basic rate as a control frame instead of a high speed data frame. Yes. For this reason, when using an application that handles a large amount of data such as audio and moving images, there is also a problem in that quality degradation occurs.

  Patent Document 1 describes a data communication system that reduces deterioration in transmission quality due to packet loss when a data distribution service using multicast communication is performed in a wireless LAN. The data distribution system described in Patent Document 1 converts a multicast packet into a unicast packet in a wireless communication section using a wireless LAN, performs unicast communication, and then restores the multicast packet and distributes it to user equipment. Since such a data distribution system performs unicast communication having a retransmission processing function by ACK control in a wireless communication section in which packet loss is likely to occur, transmission quality deterioration due to packet loss can be reduced.

JP 2006-333309 A (paragraph 0009, paragraph 0026)

  However, the data distribution system described in Patent Document 1 can reduce deterioration in transmission quality due to packet loss, but does not describe a specific method for converting a multicast packet into a unicast packet. In addition, there is no description about the transfer rate of the converted packet, and if the control frame transfer rate is low, when using an application that handles a large amount of data such as audio and video, a part of the data to be transferred May not be transferred and data quality may be degraded.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a wireless relay device and a data communication method for reliably transferring data such as voice and moving images transmitted by multicast communication to a terminal without degrading data quality.

  A wireless relay device according to the present invention is a wireless relay device that transfers multicast communication data received from a network to a terminal via a wireless transmission path, and performs line control for receiving a multicast packet addressed to a multicast group from the network , A storage unit that stores an address table in which addresses of terminals participating in the multicast group are set, and an address table stored in the storage unit to refer to the multicast packet received by the line control unit. A packet conversion unit that converts the packet into a cast packet; and a radio control unit that transmits and receives packets by radio communication with the terminal. The radio control unit converts the communication data converted into a unicast packet by the packet conversion unit into a predetermined minimum Transfer to the terminal at a transfer rate that is higher than the transfer rate. And features.

  A data communication method according to the present invention is a data communication method in a wireless relay device that transfers multicast communication data received from a network to a terminal via a wireless transmission path, and transmits a multicast packet addressed to a multicast group from the network. A radio control unit that receives and refers to an address table in which addresses of terminals participating in the multicast group are set, converts the received multicast packets into unicast packets, and transmits and receives packets by radio communication with the terminals; The communication data converted into the unicast packet is transferred to the terminal at a transfer rate equal to or higher than a predetermined minimum transfer rate.

  According to the present invention, it is possible to reduce data loss due to packet loss in wireless communication and reliably transfer data such as voice and moving images transmitted by multicast communication while preventing deterioration in data quality.

It is a block diagram which shows the structure of 1st Embodiment of the radio relay apparatus by this invention. It is explanatory drawing which shows an example of the communication system containing the radio relay apparatus shown in FIG. It is explanatory drawing which shows an example of the multicast / unicast conversion with respect to a radio | wireless MAC frame. FIG. 3 is an explanatory diagram illustrating an example of an operation in which the wireless relay device illustrated in FIG. It is a block diagram which shows the principal part of the radio relay apparatus by this invention.

Embodiment 1. FIG.
FIG. 1 is a block diagram showing a configuration of a first embodiment (Embodiment 1) of a wireless relay device according to the present invention. FIG. 2 is an explanatory diagram showing an example of a communication system including the wireless relay device shown in FIG.

  First, an example of a communication system including the wireless relay device 10 according to the first embodiment of the present invention will be described with reference to FIG.

  The wireless relay device 10 performs data communication with the server 30 via the network 20 connected by wire. The server 30 is connected to a network 20 such as the Internet or a dedicated IP network. The server 30 transmits communication data such as voice and moving images in a multicast packet to the multicast group. The wireless relay device 10 is a kind of access point in the wireless LAN system.

  The wireless relay device 10 receives the multicast packet transmitted from the server 30, performs a predetermined process on the received packet, and then wirelessly transmits to the terminals (for example, the terminals 41 and 42) participating in the multicast group. Transfer unicast packets by communication. The predetermined processing performed by the wireless relay device 10 includes conversion of a packet from a multicast packet to a unicast packet, routing of wireless communication of the packet, and the like.

  The terminals 41 and 42 are participating in the multicast group, but the terminal 43 is not participating in the multicast group of the server 30. The terminals 41, 42, and 43 are information processing terminals such as a television device or a notebook personal computer having a wireless function.

  Next, the configuration of the wireless relay device 10 according to the first embodiment will be described with reference to FIG.

  The wireless relay device 10 includes a line control unit 11, a wireless control unit 12, a main control unit 13, a program storage unit 14, and a conversion table storage unit 15.

  The line control unit 11 transmits and receives packets to and from the server 30 via the network 20. The wireless control unit 12 transmits and receives packets to and from the terminal 41 and the terminal 42 using wireless communication.

  The main control unit 13 controls the line control unit 11 and the radio control unit 12. In addition, the main control unit 13 controls processing for converting a multicast packet received by the line control unit 11 into a unicast packet (hereinafter also referred to as multicast / unicast conversion), routing processing, and the like. The main control unit 13 is a CPU controlled according to a program, for example.

  The program storage unit 14 stores programs necessary for executing various controls by the main control unit 13. The conversion table storage unit 15 stores an address table to which the main control unit 13 refers to perform multicast / unicast conversion. In the address table, the MAC address of the multicast group, the MAC address of the terminals participating in the multicast group, and the like are set.

  FIG. 3 is an explanatory diagram showing an example of multicast / unicast conversion for a wireless MAC frame. With reference to FIG. 3, a detailed operation in which the wireless relay device 10 shown in FIG. 1 exchanges a multicast packet transmitted from the server 30 for a unicast packet and transmits the packet to the terminals 41 and 42 will be described.

  First, the server 30 transmits communication data such as voice and moving images in a multicast packet to the multicast group. The line control unit 11 of the wireless relay device 10 receives the multicast packet transmitted by the server 30 from the network 20. The line control unit 11 passes the received multicast packet to the main control unit 13.

  Here, the upper table in FIG. 3 shows the basic format of the wireless MAC frame defined in the IEEE 802.11 recommendation. The lower table in FIG. 3 is an excerpt of a part related to multicast / unicast conversion performed by the wireless relay device shown in FIG. 1 in the basic format of the wireless MAC frame defined in the IEEE 802.11 recommendation. Show.

  The format of the wireless MAC frame shown in FIG. 3 includes four areas (corresponding to addresses 1 to 4) for storing addresses. Of the four areas, address 1 stores the destination address of the packet, address 2 stores the address of the wireless transmission station, and address 3 stores the source address of the packet. The main control unit 13 can distinguish whether the packet is a multicast packet or a unicast packet based on the destination address stored in the address 1. Specifically, for example, the main control unit 13 confirms the value of the first bit of each address to determine whether the destination address is a multicast address or a unicast address, and as a result, the packet Is a multicast packet or a unicast packet.

  In the MAC frame of the multicast packet received by the main control unit 13 from the line control unit 11, the MAC address of the multicast group is stored at address 1 as the destination address of the communication data. Address 2 stores the MAC address (BSSID: Basic Service Set Identifier) of the wireless relay device 10 as the address of the wireless transmission station. The address 3 stores the MAC address of the server 30 as a transmission source address of communication data.

  The main control unit 13 converts the multicast packet received from the line control unit 11 into a unicast packet. Specifically, the main control unit 13 refers to the address table stored in the conversion table storage unit 15 and determines the destination address stored in the address 1 from the MAC address of the multicast group to the terminal 41 and the terminal 42. Change to the MAC address. By storing the MAC addresses of the terminal 41 and the terminal 42, which are unicast MAC addresses, in the address 1, a multicast packet destined for the multicast group is converted into a unicast packet destined for the terminals 41 and 42.

  Here, an operation in which the main control unit 13 registers the MAC addresses of the terminals 41 and 42 in the address table or deletes them from the address table will be described.

  FIG. 4 is an explanatory diagram illustrating an example of an operation in which the wireless relay device illustrated in FIG. 1 registers or deletes an entry in the address table.

  Between the server 30 and the network 20 and the terminals 41 and 42, control regarding the multicast group is performed by an IP multicast protocol control message. The IP multicast protocol control message includes, for example, a “join” message indicating that the terminal joins the multicast group and a “leave” message indicating that the terminal leaves the multicast group to which the terminal has joined. The “join” message and the “leave” message may be transmitted periodically. The IP multicast protocol includes IPv4 Internet Group Management Protocol (IGMP), IEEE 802.1GMRP (GARP Multicast Registration Protocol) defined by the IEEE 802.1 Recommendation, IPv6 MLD (Multicast Listener Discovery), and the like.

  The main control unit 13 of the wireless relay device 10 controls the wireless control unit 12 to snoop “join” message and “leave” message transmitted from the terminals 41, 42, 43 to the server 20.

  When the main control unit 13 detects the “join” message, the MAC address of the transmission source terminal of the “join” message (for example, the MAC address of the terminal 41 or the terminal 42) and the IP address of the participation destination (for example, a certain multicast group) Assigned IP address). The main control unit 13 derives a MAC address (MAC address of the multicast group) corresponding to the IP address from the extracted IP address of the multicast group of the participation destination. Then, the main control unit 13 refers to the address table stored in the conversion table storage unit 15 and when the MAC address of the transmission source terminal is not registered in the multicast group entry indicated by the derived MAC address, The MAC address of the transmission source terminal is registered in the entry.

  When the main control unit 13 detects the “leave” message, the MAC address of the transmission source terminal of the “leave” message (for example, the MAC address of the terminal 41 or the terminal 42) and the IP address of the withdrawal destination (for example, a certain multicast group) Assigned IP address). The main control unit 13 derives the MAC address (MAC address of the multicast group) corresponding to the IP address from the extracted multicast group IP address of the withdrawal destination. The main control unit 13 refers to the address table stored in the conversion table storage unit 15, and when the MAC address of the transmission source terminal is registered in the multicast group entry indicated by the derived MAC address, Delete the MAC address of the source terminal from the entry.

  Therefore, when the main control unit 13 snoops the “join” message and the “leave” message, the MAC addresses of the terminals participating in the multicast group, that is, the MAC addresses of the terminals 41 and 42 are stored in the address table. The The main control unit 13 can obtain the MAC addresses of the terminal 41 and the terminal 42 with reference to the address table stored in the conversion table storage unit.

  In such a wireless relay device 10, multicast / unicast conversion can be easily performed only by changing the MAC address of the MAC frame without changing the upper packet with respect to the multicast packet of the communication data. Can do.

  Next, an operation when the wireless relay apparatus 10 shown in FIG. 1 transmits a multicast / unicast converted unicast packet to the terminals 41 and 42 by wireless communication will be described.

  In the IEEE recommendation, a parameter “Supported rates” for setting a transfer rate supported by the wireless LAN is defined. All transfer rates supported by the wireless relay device 10 are set to “Supported rates” of the wireless LAN.

  Here, the main control unit 13 of the wireless relay device 10 presets a predetermined minimum transfer rate in a parameter of “Supported rates” of the wireless LAN in advance. Specifically, the main control unit 13 sets a transfer rate that satisfies a transfer rate necessary for guaranteeing a certain quality in data transfer such as voice and moving images as a minimum transfer rate in “Supported rates” of the wireless LAN. To do. The transfer rate required to guarantee a certain quality in data transfer such as voice and video is faster than the low transfer rate (basic rate) generally used for sending multicast packets in wireless LAN. It is. Then, the wireless relay device 10 controls the wireless control unit 12 to transmit unicast packets to the terminals 41 and 42 at a transfer rate equal to or higher than the set minimum transfer rate.

  In such a wireless relay device 10, the minimum transfer rate is fixed to a transfer rate at a level that can guarantee data quality such as voice and moving images, and packets are transmitted at a transfer rate higher than the fixed minimum transfer rate. It is possible to prevent deterioration of data quality that easily occurs during transfer. And since the minimum transfer rate is fixed in the radio relay apparatus 10, the terminal side does not require a measure relating to the transfer rate, and the user's effort can be reduced.

  In addition, in such a wireless relay device 10, communication data is not converted to a wireless LAN multicast packet without a retransmission function, but is converted into a wireless LAN unicast packet with a retransmission function and transmitted, so that packet loss occurs. In this case, it is possible to prevent a situation in which lost packet information is lost without reaching the terminals 41 and 42. Therefore, it is possible to reduce the influence of packet loss in multicast transfer that occupies a high proportion of the packet rate of the entire network, and to improve convenience.

Embodiment 2. FIG.
A second embodiment (embodiment) of the wireless relay device according to the present invention will be described. The configuration of the wireless relay device of the second embodiment is the same as that of the wireless relay device 10 shown in FIG.

  According to the IEEE 802.11 recommendation, it is permitted to add unique information to the end of the frame body of the management frame of the wireless MAC frame. Therefore, in the wireless relay device of the second embodiment, without changing the minimum transfer rate in the “Supported rates” of the wireless LAN, at the end of the frame body of the wireless MAC frame subjected to multicast / unicast conversion, A new minimum transfer rate setting is added. That is, in the wireless MAC frame converted into the unicast packet, the main control unit 13 performs transfer necessary for guaranteeing a certain quality in the data transfer such as voice / moving image with respect to the end of the frame body of the management frame. A new setting is made to set the transfer rate satisfying the speed as the minimum transfer rate.

  In such a wireless relay device, the minimum transfer rate is not set to be changed in the “Supported rates” of the wireless LAN. Therefore, in the normal unicast frame, the transfer rate is not changed during transmission. Then, only when a unicast frame subjected to multicast / unicast conversion is transmitted, the frame can be transferred at a transfer rate that is equal to or higher than the minimum transfer rate that guarantees a certain quality in the data transfer such as voice / moving image.

  In the wireless relay devices of the first and second embodiments, the configuration example in the wireless LAN network has been shown. However, when packet loss occurs, the multicast packet transfer does not have a means for dealing with the lost packet and does not have a unit. The transfer of the cast packet may be configured in another network provided with a means for dealing with the lost packet (for example, a retransmission function). Examples of other networks include networks such as Bluetooth (registered trademark), WiMAX (Worldwide Interoperability for Microwave Access), and PLC (Power Line Communication).

  FIG. 5 is a block diagram showing a main part of the wireless relay device according to the present invention. As shown in FIG. 5, the wireless relay device 1 (corresponding to the wireless relay device 10 shown in FIG. 1) receives multicast communication data received from the network 2 (corresponding to the network 20 shown in FIG. 1) as a wireless transmission path. 1 is a wireless relay device that transfers to a terminal 3 (corresponding to the terminal 41 shown in FIG. 2), and receives a multicast packet addressed to a multicast group from the network 2 (line control unit shown in FIG. 1). 11), a storage unit 5 (corresponding to the conversion table storage unit 15 shown in FIG. 1) for storing an address table in which addresses of terminals participating in the multicast group are set, and a storage unit 5 Referring to the address table, the packet converter 6 (see FIG. 4) converts the multicast packet received by the line controller 4 into a unicast packet. 1) and a radio control unit 7 (corresponding to the radio control unit 12 shown in FIG. 1) for transmitting and receiving packets by wireless communication with the terminal 3, and the radio control unit 7 The communication data converted into the unicast packet by the conversion unit 6 is configured to be transferred to the terminal 3 at a transfer rate equal to or higher than a predetermined minimum transfer rate.

  Further, in each of the above embodiments, wireless relay apparatuses as shown in the following (1) to (4) are also disclosed.

(1) For the minimum transfer rate supported during wireless communication, a transfer rate that guarantees data quality such as voice and video is set in advance (for example, realized by setting “Supported rates” in the first embodiment) .) A wireless relay device, wherein the wireless control unit transfers the communication data converted into the unicast packet to the terminal at a transfer rate equal to or higher than the minimum transfer rate according to the setting of the wireless relay device.

(2) When converting a multicast packet into a unicast packet, the packet conversion unit transfers the minimum transfer rate that guarantees the data quality of voice or video to the frame body of the wireless MAC frame of the unicast packet. The wireless control unit transfers the communication data converted into the unicast packet to the terminal at a transfer rate equal to or higher than the minimum transfer rate according to the setting added by the packet switching unit (for example, Realized by the operation of the wireless relay device of the second embodiment.) Wireless relay device.

(3) The packet relay unit is a wireless relay device that changes a destination address for a wireless MAC frame of a multicast packet from a MAC address of the multicast group to a MAC address of a terminal participating in the multicast group.

(4) Among IP multicast protocols transmitted and received between the terminal and the network, a predetermined control message indicating the participation or withdrawal of the terminal in the multicast group (for example, “join” message or “ a monitoring unit (corresponding to the main control unit 13 shown in FIG. 1), and the monitoring unit is stored in the storage unit based on information extracted from the predetermined control message snooping A wireless relay device that updates information in an address table.

  The present invention can be applied to a moving image distribution system that distributes audio and moving images via a network such as the Internet.

DESCRIPTION OF SYMBOLS 1 Wireless relay apparatus 2 Network network 3 Terminal 4 Line control part 5 Storage part 6 Packet conversion part 7 Wireless control part 10 Wireless relay apparatus 11 Line control part 12 Wireless control part 13 Main control part 14 Program storage part 15 Conversion table storage part 20 Network 30 server 41, 42, 43 terminal

Claims (7)

A wireless relay device that transfers multicast communication data received from a network to a terminal via a wireless transmission path,
A line control unit for receiving a multicast packet addressed to a multicast group from the network;
A storage unit for storing an address table in which addresses of terminals participating in the multicast group are set;
A packet conversion unit that converts a multicast packet received by the line control unit into a unicast packet with reference to an address table stored in the storage unit;
A wireless control unit that performs transmission and reception of packets by wireless communication with the terminal,
The wireless control unit transfers the communication data converted into a unicast packet by the packet conversion unit to the terminal at a transfer rate equal to or higher than a predetermined minimum transfer rate. A wireless relay device in which a transfer rate that guarantees data quality such as voice and video is set in advance for the minimum transfer rate supported during wireless communication,
The radio relay apparatus according to claim 1, wherein the radio control unit transfers the communication data converted into the unicast packet to the terminal at a transfer rate equal to or higher than a minimum transfer rate according to the setting of the radio relay apparatus. When converting a multicast packet into a unicast packet, the packet conversion unit sets the transfer rate that guarantees the data quality of voice, video, etc. to the minimum transfer rate in the frame body of the management frame of the wireless MAC frame of the unicast packet Add settings,
The radio relay apparatus according to claim 1, wherein the radio control unit transfers the communication data converted into the unicast packet to the terminal at a transfer rate equal to or higher than a minimum transfer rate according to the setting added by the packet exchange unit. The packet conversion unit changes the destination address for the wireless MAC frame of the multicast packet from the MAC address of the multicast group to the MAC address of the terminal participating in the multicast group. The wireless relay device according to any one of the above. Among IP multicast protocols transmitted and received between a terminal and a network, a monitoring unit for snooping a predetermined control message indicating participation or withdrawal of a terminal in a multicast group is provided,
The said monitoring part updates the information of the address table stored in the storage part based on the information extracted from the predetermined | prescribed control message snooped. The any one of Claims 1-4 Wireless relay device. A data communication method in a wireless relay device for transferring multicast communication data received from a network to a terminal via a wireless transmission path,
Receiving a multicast packet addressed to a multicast group from the network,
With reference to an address table in which addresses of terminals participating in the multicast group are set, the received multicast packet is converted into a unicast packet,
A wireless control unit that performs transmission and reception of packets by wireless communication with the terminal,
A data communication method, wherein communication data converted into a unicast packet is transferred to the terminal at a transfer rate equal to or higher than a predetermined minimum transfer rate. Set the transfer rate that guarantees data quality such as audio and video in advance as the minimum transfer rate supported during wireless communication,
The data communication method according to claim 6, wherein communication data converted into a unicast packet is transferred to a terminal at a transfer rate equal to or higher than a minimum transfer rate according to the setting.

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