EECS CSPL SEMINAR SERIES
WINTER TERM 1996


Masaaki Katayama

Masaaki Katayama

Nagoya University, Japan



January 23, 1996


Spread Slotted ALOHA System for Low Earth-Orbital (LEO) Statellite Communication Systems and Effects of Nonuniform User Distribution

Abstract -
Low earth orbital satellite communication systems are one of the hottest topics in the field of satellite communications. This type of system encounters many interesting technical issues such as receiver synchronization in the presence of large Doppler shifts, hand-off procedures between satellites, inter-satellite interference, routing through satellites, etc. Among these issues, this seminar will discuss the effects of geographically nonuniform traffic requirements on throughput performance.

Although it is a normal feature of our globe that different amounts of communication are requested in different areas, there have been very few studies on the effects of such. In this seminar, a simple, tractable mathematical model of traffic nonuniformity will be introduced. Under this model, the throughput performance of up-link (reverse-link) will be discussed. As an access scheme, Spread Slotted ALOHA, which is a combination of SSMA and S-ALOHA, will be employed. In order to improve the throughput performance, some modifications of this scheme have been proposed, such as varying the transmitting power of each user according to its position relative to the satellites or even prohibiting some terminals from transmitting. These modifications will be introduced, and numerical results showing the performance improvements will be given.


Biosketch -
Prof. Katayama, Assoc. Prof. of Nagoya University in Japan, received his Ph.D. from Osaka University, Japan, in 1986 in Communication Engineering. He has been in EECS as a visiting associate professor, from September 1995, according to the Academic Exchange Program between the School of Engineering of Nagoya University and the College of Engineering of the University of Michigan. His research interests include, Satellite and Mobile Communication Systems, Spread Spectrum Communication Systems, Traffic Control in Radio Networks, Nonlinear Modulation and Coded Modulations, and Combined Designs of Adaptive Array Antennas and Receivers.



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