Hop-by-Hop TCP over MANET

In a MANET environment, communication links are unstable due to various reasons. Error rate is higher and bandwidth is smaller than fixed networks. Running conventional TCP protocol over MANET will suffer from severe performance degradation. To handle a packet loss, conventional TCP retransmits the lost packet from its source. However, when error rate is high, it may have to take several retransmissions to deliver a packet to its destination successfully. Considering that most applications on a MANET prefer shorter packet delivery time to higher bandwidth, this paper proposes a hop-by-hop TCP protocol for MANET aiming to accelerate packet delivery. Hop-by-hop TCP makes every intermediate node in the transmission path execute a local TCP to guarantee the transmission of each packet on each link. The retransmission of a lost packet is right at the transmitting end of the link where the packet is lost. It takes less time in average to deliver a packet in a high error rate environment. The performance of our approach is evaluated by simulation using NS-2 simulator. Our experiments show that our proposed protocol outperforms TCP Reno by 25.7% in throughput and 25% reduction in average packet delivery time. The fairness requirement is also achieved while our proposed protocol coexists with other major TCP variants.