Data transmitting and receiving system, terminal, relay device, and data transmitting method

A terminal, connected to a relay device via an ad-hoc network, which transmits to and receives data from another terminal via the relay device, the terminal comprising:

• a transmitting and receiving unit configured to transmit and receive data and an observation packet used for observing transmission quality;
• a transmission quality managing unit configured to write degraded state information in the observation packet received by the transmitting and receiving unit from the another terminal via the rely device, and to cause the transmitting and receiving unit to transmit, via the relay device, the observation packet in which the degraded state information is written to the another terminal, the degraded state information indicating a loss rate of the data between the terminal and the another terminal;
• and
• a reception state managing unit configured to detect a change of a reception state of the data in the transmitting and receiving unit,
• wherein, in the case where the reception state managing unit detects the change of the reception state, the transmission quality managing unit is configured to transmit a trigger packet to the another terminal via the relay device, the trigger packet indicating an instruction for transmitting a new observation packet.

A relay device, connected to a terminal via an ad-hoc network, which relays data transmitted to and received from terminals including the terminal, the relay device comprising:

• a receiving unit configured to receive an observation packet used for observing transmission quality, and data;
• a reception buffer in which the data is stored;
• a reception buffer managing unit configured to observe a loss rate of the data in the reception buffer;
• a packet information rewriting unit configured to write the loss rate into the observation packet as congested state information, the loss rate being observed by the reception buffer managing unit;
• a transmission buffer configured to store the data stored in the reception buffer on a destination basis;
• a transmission buffer managing unit configured to forward the data stored in the transmission buffer at a predetermined transmission rate on a destination basis;
• a transmitting unit configured to transmit towards a destination the data forwarded by the transmission buffer managing unit, and the observation packet;
• and
• a reception state managing unit configured to detect a change of a reception state of the data in the receiving unit, and, in the case where the change of the reception state is determined, to instruct the terminal which transmits the data so as to transmit the observation packet.

A data transmission method for a system which includes a relay device, a transmitting terminal, and a receiving terminal that are connected to an ad-hoc network, and transmits data from the transmitting terminal to the receiving terminal via the relay device, the data transmission method comprising:

• transmitting data from the transmitting terminal to the relay device towards the receiving terminal;
• relaying the data by the relay device;
• receiving the data by the receiving unit;
• transmitting an observation packet used for observing transmission quality from the transmitting terminal to the relay device towards the receiving terminal;
• receiving the observation packet by the relay device, writing a loss rate of the data in the observation packet as congested state information, and transmitting the observation packet towards the receiving terminal;
• receiving the observation packet transmitted from the relay device by the receiving terminal, writing a loss rate of the data into the observation packet as degraded state information, the data regarding between the transmitting terminal and the receiving terminal, and transmitting the observation packet towards the transmitting terminal;
• and
• calculating a transmission error rate of the data in the system by the transmitting terminal receiving the observation packet having the congested state information and the degraded state information, and subtracting the congested state information from the degraded state information included in the received observation packet.