Pawan Kumar Gupta
Articles written in Sadhana
Volume 32 Issue 3 June 2007 pp 253-275
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.