TCP with header checksum option for wireless links: An analytical approach towards performance evaluation

TCP performs poorly in wireless mobile networks due to large bit error rates. Basically, the TCP sender responds to these losses as if they were due to congestion in the network, and reduces the congestion window unnecessarily. In earlier work, it has been shown that adding a TCP header checksum is very useful in differentiating between congestion loss and corruption loss. With the modified TCP, receivers can explicitly indicate corruption of received packets by generating "Explicit Loss Notifications (ELNs)." This paper focuses on an analytical study of this modified TCP protocol. We derive an expression for the probability of a receiver generating successful ELN, assuming a generic link layer protocol for data transfer over wireless links. Next, we develop an analytical approach for TCP throughput evaluation under the modified scheme. We compare the throughput results obtained by analysis and simulation, and find very close agreement between the two sets. We also compare the performance of the modified scheme with the standard NewReno TCP, and find considerable improvement in data throughput over wireless links.