TCP interprets packet loss as congestion and slows down. On the other hand in Ad-Hoc networks, a packet can be lost due to channel errors. In this case the node should try to transmit at full speed, not slow down. The ATCP is a sublayer between the IP and transport layer. When it detects a packet loss due to the channel, it simply sets the transmission window of TCP to 0, until it manages to correctly deliver the packet.