JP2009267978A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system in which the quality of call is improved, by improving the tolerance to data loss. <P>SOLUTION: A wireless terminal A has a function for duplicating an RTP voice packet which is to be transmitted, and a wireless terminal E has a function for determining an overlap from a sequence number of the RTP voice packet. Voice data of the wireless terminal A are duplicated as RTP (Real-time Transfer Protocol) voice packets and is transferred over an ad-hoc wireless network as separate IP packets. The wireless terminal E determines overlapping, from the sequence numbers of the packets received; and when packets overlap, the packet is discarded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication system that sequentially transfers packet data between a plurality of nodes in a multi-hop wireless mesh network (ad hoc wireless network), and a wireless terminal device used in the system.

  Various environments and situations such as large-scale disaster areas, construction / construction sites, event venues, etc. have been requested to construct a private and temporary telephone network without using a public network for communication between workers. It has been proposed (see, for example, Patent Documents 1 and 2). As a system that satisfies such a demand, an ad hoc wireless network that can form a communication link autonomously between terminals is attracting attention.

An ad hoc wireless network can autonomously construct an IP network by exchanging link relations between terminals, and then can make a voice call using VoIP (Voice over IP) technology. While having such an advantage, IP (Internet Protocol) packets including voice data and various management information are transmitted via a wireless section, and therefore packet loss due to link quality deterioration is likely to occur. In particular, calls are vulnerable to packet loss, and there is a problem that the quality of voice deteriorates and reliability decreases.
JP 2006-108978 A Japanese Patent Laid-Open No. 10-257064

  In an existing ad hoc wireless network, packets are sequentially relayed and transferred from a transmitting end to a receiving end via a wireless link between terminals, so that data loss due to a link failure is likely to occur. For such data loss, a recovery method using retransmission processing at the data link layer or end-to-end retransmission processing at the transport layer is conceivable, but retransmission processing is performed without losing the real-time nature of the voice data. It is difficult.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wireless communication system that has improved resistance to data loss and improved call quality.

  In order to achieve the above object, according to one aspect of the present invention, there is provided a wireless communication system in which an ad hoc wireless network is formed by a plurality of wireless terminal devices and IP packets including voice data are transmitted through the ad hoc wireless network. The plurality of wireless terminal devices convert a transmission voice into data, generates the IP packet, and transmits the IP packet to the ad hoc wireless network; and a voice from the IP packet received via the ad hoc wireless network. A reception processing unit for reproducing and outputting, wherein the transmission processing unit further duplicates the generated IP packet and sends it to the ad hoc wireless network, and the reception processing unit arrives via the ad hoc wireless network. One of the multiple IP packets that contain the same sequence number Wireless communication system, characterized in that there is provided.

  By taking such a measure, the IP packet is transferred to the destination along a plurality of routes in the ad hoc wireless network, so that it is possible to increase the resistance to data loss.

  According to the present invention, it is possible to provide a radio communication system with improved resistance to data loss and improved call quality.

FIG. 1 is a system diagram showing an embodiment of a wireless communication system according to the present invention. This system includes a plurality of wireless terminals 11 to 17 to form an ad hoc wireless network. Communication paths between the wireless terminals 11 to 17 are indicated by double arrows. This communication path is not fixed and is updated and set according to the passage of time and the movement of the individual wireless terminals 11 to 17. In this type of network, multi-hop transmission is performed in which a wireless packet passes through one or more wireless terminals from its transmission source to its destination.
FIG. 2 is a functional block diagram showing an embodiment of the wireless terminals 11 to 17 in FIG. In FIG. 4, the voice given to the voice input unit 25 is encoded by the encoder 26, then digitally modulated by the transmission unit 27, and radiated from the antenna 20 via the hybrid circuit 21. On the other hand, the radio signal arriving at the antenna 20 is input to the receiving unit 22 via the hybrid circuit 21 and is received and demodulated. The obtained signal is subjected to processing such as packet decomposition by the decoder 23, and is then supplied to the audio output unit 24, where the audio is amplified. The functions related to the processing in these functional blocks, particularly the functions related to the packet processing in the encoder 26, are comprehensively controlled by the control unit 28. Next, the operation of the above configuration will be described.

[First Embodiment]
FIG. 3 is a schematic diagram showing a packet transmission path in the first embodiment of the wireless transmission system according to the present invention. In FIG. 3, reference signs A to E are wireless terminals constituting the ad hoc wireless network, and are any of the wireless terminals 11 to 16 in FIG. 1. Here, the wireless terminal A is a transmitting terminal, the wireless terminal E is a receiving terminal, and the wireless terminals B, C, and D are relay terminals.

  The wireless terminal A has a function of copying the RTP voice packet to be transmitted, and the wireless terminal E has a function of performing duplication determination from the sequence number of the RTP voice packet. The voice data of the wireless terminal A is copied as an RTP (Real-time Transfer Protocol) voice packet and transferred as a separate IP packet on the ad hoc wireless network. The wireless terminal E performs duplication determination from the sequence number of the received packet, and discards it if there is duplication.

  In FIG. 3, voice data obtained by converting transmitted voice into data is converted into RTP packets, further duplicated, and sent to the ad hoc wireless network as a plurality of IP packets. Even when a packet loss occurs in the midway transfer path, the wireless terminal E can reproduce the audio data if any of the duplicated packets arrive. In this way, the voice data is duplicated and distributed on the transmitting radio terminal side, and by selecting and receiving the voice data on the receiving radio terminal side, the redundancy of the data can be secured, and the real-time property is not impaired. Reliability can be improved.

[Second Embodiment]
FIG. 4 is a schematic diagram showing a packet transmission path in the second embodiment of the wireless transmission system according to the present invention. Similarly to FIG. 3, the wireless terminals A to E form an ad hoc wireless network, where the wireless terminal A is a transmitting terminal, the wireless terminal E is a receiving terminal, and the wireless terminals B, C, and D are relay terminals. The wireless terminal A has a function of copying the RTP voice packet to be transmitted, and the wireless terminal E has a function of performing duplication determination from the sequence number of the RTP voice packet.

  The voice data of the wireless terminal A is duplicated as an RTP voice packet and transferred over the ad hoc wireless network as separate IP packets addressed to different UDP ports. The wireless terminal E performs duplication determination from the sequence number of the received packet, and discards it if there is duplication. Even in this case, even when a packet loss occurs in the transfer path on the way, audio data can be reproduced if any of the duplicated packets arrives.

[Third Embodiment]
FIG. 5 is a schematic diagram showing a packet transmission path in the third embodiment of the wireless transmission system according to the present invention. In FIG. 5, wireless terminals A, B, C, D, E, B ′, C ′, and D ′ form an ad hoc wireless network, and the transmitting terminal and the receiving terminal have a plurality of communication interfaces having different frequency channels. The wireless terminals B, C, D, E, B ′, C ′, and D ′ on the route need only have at least an interface for relaying between transmission and reception, and even if all the wireless terminals have a plurality of interfaces. good.

  The voice data of the wireless terminal A is copied as an RTP voice packet and transferred over the ad hoc wireless network as an IP packet on a separate communication interface. The wireless terminal E performs duplication determination from the sequence number of the packet received from each communication interface, and discards this if there is duplication. Even in this case, even when a packet loss occurs in the transfer path on the way, audio data can be reproduced if any of the duplicated packets arrives.

[Fourth Embodiment]
FIG. 6 is a schematic diagram showing packet transmission paths in the fourth embodiment of the wireless transmission system according to the present invention. The wireless terminals A to G form an ad hoc wireless network and are wireless terminals. The wireless terminal A is a transmitting terminal, the wireless terminal E is a receiving terminal, and the wireless terminals B, C, D, and F are relay terminals. The wireless terminal G is a receiving terminal different from the wireless terminal A that receives the broadcast voice, and is an adjacent node of the wireless terminal A.

  The receiving terminal E can recognize the existence of the wireless terminals D and G adjacent by one hop by flooding the route information exchange message. Further, the directly adjacent transfer wireless terminal D on the route from the transmission destination can be recognized from the route information table by the routing protocol. The voice data from the transmitting terminal A is broadcast data, and the wireless terminals E and G receive the same voice data from different paths.

  The receiving terminal E issues a voice data transfer request to the receiving terminal G excluding the wireless terminal D on the transfer path in advance. Upon receiving the transfer request, G transfers the incoming voice packet addressed to itself to the requesting E. The wireless terminal E determines duplication by the sequence number from the data including the transferred data and the data received by the own wireless terminal. If there is duplication, the wireless terminal E discards it and reproduces the data.

[Fifth Embodiment]
FIG. 7 is a schematic diagram showing packet transmission paths in the fifth embodiment of the wireless transmission system according to the present invention. Wireless terminals A, B, C, D, E, B ′, C ′, D ′ form an ad hoc wireless network, A is a transmitting terminal, E is a receiving terminal, B, C, D and B ′, C ′, D ′ is a wireless terminal on the set transfer path. The voice data of the wireless terminal A is copied as an RTP packet, set to a different UDP port number, and transferred via a separate route to the wireless terminal E obtained from the route information table. The receiving terminal E compares sequence numbers from RTP packets destined for different UDP port numbers of the same transmission source, discards duplicates, complements the data, and reproduces them.

  As described above, in each embodiment, the IP packet is duplicated in the wireless terminal that is the transmission source of the IP packet, and transferred to the same destination via different transfer paths in the ad hoc wireless network. In a receiving terminal that has received a plurality of IP packets, duplication is determined from the sequence number of the received packets, and if there is duplication, it is discarded. In this way, even if a packet loss occurs in the midway transfer route, the voice data can be reproduced if any of the duplicated packets arrives. Therefore, it is possible to provide a wireless communication system with improved resistance to data loss and improved call quality.

  In addition, this invention is not limited to the said embodiment, In an implementation stage, a component can be deform | transformed and embodied in the range which does not deviate from the summary. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a system diagram showing an embodiment of a wireless communication system according to the present invention. The functional block diagram which shows embodiment of the radio | wireless terminals 11-17 of FIG. The schematic diagram which shows the packet transmission path | route in 1st Embodiment of the radio | wireless transmission system in connection with this invention. The schematic diagram which shows the packet transmission path | route in 2nd Embodiment of the radio | wireless transmission system in connection with this invention. The schematic diagram which shows the packet transmission path | route in 3rd Embodiment of the radio | wireless transmission system in connection with this invention. The schematic diagram which shows the packet transmission path | route in 4th Embodiment of the radio | wireless transmission system in connection with this invention. The schematic diagram which shows the packet transmission path | route in 5th Embodiment of the radio | wireless transmission system in connection with this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11-17 ... Wireless terminal, 20 ... Antenna, 21 ... Hybrid circuit, 22 ... Reception part, 23 ... Decoder, 24 ... Audio | voice output part, 25 ... Audio | voice input part, 26 ... Encoder, 27 ... Transmission part, 28 ... Control part

Claims (6)

A wireless communication system that forms an ad hoc wireless network by a plurality of wireless terminal devices and transmits IP (Internet Protocol) packets including voice data through the ad hoc wireless network,
The plurality of wireless terminal devices are:
A transmission processing unit that converts transmission voice into data, generates the IP packet, and transmits the packet to the ad hoc wireless network;
A reception processing unit for reproducing and outputting voice from the IP packet received via the ad hoc wireless network,
The transmission processing unit further duplicates the generated IP packet and sends it to the ad hoc wireless network,
The wireless communication system, wherein the reception processing unit leaves one of a plurality of IP packets including the same sequence number that arrives via the ad hoc wireless network and discards the other. The wireless communication system according to claim 1, wherein the reception processing unit processes only a first-arrival IP packet among the plurality of IP packets. The reception processing unit has a plurality of predetermined UDP (User Datagram Protocol) port numbers,
2. The wireless communication system according to claim 1, wherein the transmission processing unit transmits the duplicated IP packet as separate IP packets addressed to the predetermined plurality of port numbers. The transmission processing unit includes a plurality of communication interfaces having different physical interfaces, and sends the duplicated IP packet to the ad hoc wireless network via the plurality of communication interfaces. Wireless communication system. 2. The reception processing unit recognizes an adjacent node which is an adjacent wireless terminal device, and requests retransmission of the IP packet to an adjacent node not on a transmission route of the IP packet. Wireless communication system. The plurality of wireless terminal devices recognize a transfer route in the ad hoc wireless network by a routing protocol, and the duplicated IP packet is sent to the same reception port via different transfer routes. Item 2. The wireless communication system according to Item 1.

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