Improving TCP Performance In The Wireless Environment

With the emergence of wireless technologies, many relevant issues come along with it. Because of the essential differences between the characteristic of wired and wireless network, some traditional protocol need to be reviewed in more detail. TCP is particular important among these. The main problem is that the congestion control mechanism in the design of TCP deems all packet loss as the result of the congestion. But, in fact, the error packet loss during communication comes from the high error rate of wireless environment. Whenever the TCP sender receives a loss event, it tends to conclude that the packet loss as a kind of congestion packet loss which comes from congestion, and tries to reduce the congestion window size, and therefore reduce the throughput.In this paper, we discuss the shortcomings of TCP's behavior in wireless environment, including three ones: (1) the protocol's error detection mechanism, which does not distinguish different types of errors and thus does not suffice for wireless environment; (2) the error recovery, which is not responsive to the distinctive characteristics of wireless networks; (3) the protocol strategy, which does not consider the tradeoff between performance measures such as throughput and energy consumption.Then, we describe and evaluate some design alternatives and related work that address this problem, including the end to end approach, the split connection approach and the link layer approach. We introduce the Snoop protocol in detail and a new enhancement to TCP base on the previously proposed schemes. Partial acknowledgement, TCP-Probing and Freeze-TCP is introduced to improve the performance of TCP.The performance of proposed method has been simulated by suing the network simulator OPNET. It has been shown that the throughput of the proposed method has been largely improved compared to TCP New Reno. Then we evaluate the three versions of TCP: Tahoe, Reno and New Reno which behave differently in wireless networks with energy efficiency. Finally, we evaluate the energy efficiency of the propose method, and compared it with Tahoe, Reno and New Reno.