Patent ID: 7885264

Claim:
A method for controlling retransmission of data comprising: transmitting, from a first communications device to a second communications device, a first data packet comprising a data part, a data sequence number, and a transmission sequence number, wherein the data part stores the data, the data being divided into a plurality of divided data blocks, wherein the data sequence number indicates the order of each divided data block in relation to each other of the plurality of divided data blocks, and wherein the transmission sequence number indicates the transmission order of the first data packet; when the first data packet is received by the second communications device, transmitting from the second communications device to the first communications device an acknowledgement packet acknowledging receipt of the first data packet, wherein the acknowledgement packet comprises a received transmission sequence number of the first data packet, a next data sequence number, and reception status information, wherein the received transmission sequence number indicates the transmission sequence number received immediately prior to transmitting the acknowledgement packet, wherein the next data sequence number indicates the data sequence number that the second communications device should receive next, and is a number obtained by adding 1 to the value of the highest data sequence number from among consecutive data sequence numbers already received, wherein the reception status information indicates the reception status of the data sequence numbers after the received next data sequence number up to a value of the highest of the received data sequence numbers, each of the received data sequence numbers corresponding to a divided data block of the plurality of divided data blocks, wherein the reception status information indicates the reception status of the data sequence numbers in a bit string, and wherein each bit of the bit string indicates whether each divided data block has been received or not; and specifying and transmitting, by the first communications device, each divided data block corresponding to a data sequence number that requires retransmission, the selection of the divided data block requiring retransmission being based on the reception status information received from the acknowledgement packet.