Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Improving TCP Performance over Wireless Ad Hoc Networks with Busy Tone Assisted Scheme | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2006 Article ID 51610 Pages 1-11 DOI WCN 2006 51610 Improving TCP Performance over Wireless Ad Hoc Networks with Busy Tone Assisted Scheme Qi He 1 Lin Cai 2 Xuemin Sherman Shen 3 and Pinhan Ho3 1 Research In Motion RIM Ottawa ON Canada K2K3K2 2 Department of Electrical and Computer Engineering Faculty of Engineering University of Victoria Victoria BC Canada V8W 3P6 3 Department of Electrical and Computer Engineering Faculty of Engineering University of Waterloo Waterloo ON Canada N2L 3G1 Received 1 August 2005 Revised 29 December 2005 Accepted 29 December 2005 It is well known that transmission control protocol TCP performance degrades severely in IEEE wireless ad hoc networks. We first identify two critical issues leading to the TCP performance degradation 1 unreliable broadcast since broadcast frames are transmitted without the request-to-send and clear-to-send RTS CTS dialog and Data ACK handshake so they are vulnerable to the hidden terminal problem and 2 false link failure which occurs when a node cannot successfully transmit data temporarily due to medium contention. We then propose a scheme to use a narrow-bandwidth out-of-band busy tone channel to make reservation for broadcast and link error detection frames only. The proposed scheme is simple and power efficient because only the sender needs to transmit two short messages in the busy tone channel before sending broadcast or link error detection frames in the data channel. Analytical results show that the proposed scheme can dramatically reduce the collision probability of broadcast and link error detection frames. Extensive simulations with different network topologies further demonstrate that the proposed scheme can improve TCP throughput by 23 to 150 depending on user mobility and effectively enhance both short-term and long-term fairness among coexisting TCP flows in multihop wireless ad
