Manuscript received November 3;
1986;
revised August 17;
1987 and October 5;
1987. Paper recommended by Past Associate Editor;
A. Ephremides. This work was supported by the Air Force Office of Scientific Research under Contract 2F49620-87-(3-0079. The authors are with the Department of Electrical Engineering and Computer Science;
The University of Michigan;
Ann Arbor;
MI 48109-2122. IEEE Log Number 8719058;