TCP congestion control for various networks in wireline or wireless environments has been widely discussed. Many research studies have focused on making TCP more sensitive to network congestion by adding explicit notifications to TCP connections or by letting the intermediate nodes in the network join in TCP congestion control. In GPRS/EGPRS systems and other 3G cellular networks, the radio network controller chooses from, among several channel coders, according to the signal to interference ratio. Hence, the channel data rate that an individual user experiences is time-dependent and variable. In this paper, we propose a TCP window control mechanism that adapts to variable channel data rates. Our simulations show that the window adaptive TCP decreases the buffer occupancy and packet transmission delay, and achieves better throughput utilization when compared with the standard TCP Tahoe version and the Reno version.