Manuscript received May 14;
1987;
revised March 23;
1988. Paper recommended by Associate Editor;
D.A . Castanon. This work was supported by the National Science Foundation under Grant ECS-8517708. R. Agrawal and D. Teneketzis are with the Department of Electrical Engineering and Computer Science and the Communications and Signal Processing Laboratory;
University of Michigan;
Ann Arbor;
MI 48109. M. V. Hegde is with the Department of Electrical and Computer Engineering;
Louisiana State University;
Baton Rouge;
LA 70803. IEEE Log Number 8822541;