Acknowledgment (ACK) Pace for Maximum Throughput over

Asymmetric Space-Internet Links

Ruhai Wang (王如海), Ph.D.

Department of Electrical Engineering

Lamar University

Beaumont, Texas, USA

{wang@ee.lamar.edu}

时间：2007年1月10日 上午10：30-12：00

地点：FIT 1-312

Abstract

The acknowledgement (ACK) strategy of Transmission Control Protocol (TCP) has been modified to delay the ACKs for a configurable period of time that is related to the round-trip time (RTT) to improve its performance over asymmetric links such as in space communications. A general relationship between the asymmetric channel ratio and the optimal ACK frequency to achieve maximum throughput is not available. In this talk, we discuss the optimal ACK frequency with respect to the channel RTT to achieve the maximum throughput over various asymmetric space communication links using a test-bed. We found that when the asymmetric channel ratio is as high as about 100/1, the optimal ACK frequency must be increased with an increase in asymmetric ratio to complement the impact of the reduction of ACK channel rate. As a rule of thumb, every two-fold increase in asymmetric ratio requires the optimal ACK frequency to be increased by one ACK per RTT. A regression model was built to reflect the relationship between the optimal ACK frequency and the asymmetric channel ratio and has been validated.

Dr. Wang has served as an Assistant Professor in Department of Electrical Engineering at Lamar University, Texas, USA, since 2002. He received his PhD in Electrical Engineering from New Mexico State University, USA, in 2001. Dr. Wang’s research interests are in computer networks and communication systems with emphases on wireless and space Internet, design/testing of Internet architecture and protocols, network modeling and performance evaluation. He has published about 40 papers in international journals and conferences proceedings. He currently serves as an editor for a few international journals. He has also served as one of the TPC co-chairs for IEEE ICC 2007 Wireless Communications Symposium.

Selected Recent Publications Related to the Talk

1.S. Horan and R. Wang, “Design of a space channel simulator using virtual instruments software,” IEEE Transactions on Instrumentation and Measurement, vol. 51. No. 5, October 2002.

2.R. Wang and S. Horan, “The impact of Van Jacobson Header Compression on TCP/IP throughput performance over lossy space channels,” IEEE Transactions on Aerospace and Electronic Systems, vol. 41, No. 2, April 2005.

3.R. Wang, B. Gutha, S. Horan, Y. Xiao, and Bo Sun, “Which transmission mechanism is best for space Internet: window-based, rate-based, or a hybrid of the two?” IEEE Wireless Communications, vol. 12, No. 6, December 2005.

4.R. Wang, S. Horan, and B. Tian, “Optimal acknowledgement frequency for maximum throughput over asymmetric space-Internet links,” IEEE Transactions on Aerospace and Electronic Systems, vol. 42, No. 4, October 2006.

5.R. Wang, B. Gutha, and Paradesh Kumar Rapet, “Comparative analysis of window-based and rate-based transmission control mechanisms over point-to-point space communication links,” IEEE Transactions on Aerospace and Electronic Systems, December 2007 (to appear).