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Multihop wireless networks based on the IEEE 802.11 MAC protocol are promising for ad hoc networks in small scale today. The 802.11 protocol minimizes the well-known hidden node problem but does not eliminate it completely. Consequently, the end-to-end bandwidth utilization may be severely compromised if the involved protocols do not interact smoothly. In particular, the TCP protocol does not manage to obtain efficient bandwidth utilization because its congestion control mechanism is not tailored to such a complex environment. The main problems with TCP in such networks are the excessive amount of both spurious retransmissions and contentions between DATA and acknowledgment (ACK) packets for the transmission medium. In this paper, we propose a dynamic adaptive strategy for minimizing the number of ACK packets in transit and mitigating spurious retransmissions. Using this strategy, the receiver adjusts itself to the wireless channel condition by delaying more ACK packets when the channel is in good condition and less otherwise. Our technique not only improves bandwidth utilization but also reduces energy consumption by retransmitting much less than a regular TCP does. Extensive simulation evaluations show that our scheme provides very good enhancements in a variety of scenarios. I. INTRODUCTION The Transport Control Protocol (TCP) is the most widely deployed transport protocol in the Internet today. TCP has been successful due to its robustness in dealing with dynamic changes in the network traffic conditions and providing reliability on an end-to-end basis. This wide acceptance has driven the development of a great deal of applications for TCP, which motivates the extension of this protocol for wireless networks. These networks pose some critical challenges to TCP since it was not originally designed to work in such complex environments, where the level of bit error rate (BER) due to the physical medium is not negligible. High levels of mobility may further degrade the end-to-end performance because TCP reduces its sending rate whenever it perceives a dropped packet. CR Categories andWe do not address mobility related issues in this paper, since it has been investigated in many past work [1]- [5], and also because we target scenarios in which the level of mobility is relatively low (pedestrian movement). The disturbance of such movements should not be too much disruptive to the transport protocol. Nonetheless, our technique is expected to work satisfactorily under a moderate level of mobility. In fact, this paper investigates TCP over multihop wireless media, which has not yet been thoroughly investigated in the research community.IEEE 802.11 [6] protocol is the standard Medium Access Control (MAC) protocol for ad hoc networks, and it consists of both link and physical layer specifications. As we explained in more detail in [7], The 802.11 implements a robust link layer retransmissions strategy along with the RTS/CTS (request-tosend/clear-to-send) control frames for recovering locally (link level) most ...

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