Data transmission rate control method and system in upward vertical handover in overlay network environment

A data transmission rate control system in upward vertical handover in an overlay network environment, comprising:

• a TCP (transmission control protocol) sender;
• and
• a TCP receiver communicating with the TCP sender through a dual interface,
• wherein the TCP sender checks whether or not an retransmission timeout event occurs while performing communication according to TCP,
• wherein the TCP sender stores a sequence number of a packet having the largest sequence number among transmitting packets, and after that, performs congestion control if the retransmission timeout event occurs,
• wherein the TCP sender checks whether or not ACK (acknowledge) signal corresponding to a sequence number which is equal to or smaller than the stored sequence number is received after performing the congestion control,
• wherein the TCP sender determines to execute the upward vertical handover if the ACK signal is received,
• wherein the TCP sender calculates and sets a congestion window size of a new network when the TCP sender determines to execute the upward vertical handover,
• wherein the congestion window size of the new network is set to a product of a maximum congestion window size of an old network and a weighting factor,
• wherein the weighting factor is set by using a data capacity of a link in the old network and a data capacity of a link in the new network, and
• wherein the data capacity depends on a BDP (Bandwidth Delay Product) of the link and a buffer size of a relay device.