Paper approved by D. P. Taylor;
the Editor for Signal Design;
Modulation;
and Detection of the IEEE Communications Society. Manuscript received Februav 28;
1995;
revised June 6;
1995. This work was supported by the National Science Foundation under Grant NCR-9304185. This paper was presented in part at the 1995 IEEE 45th Vehicular Technology Conference;
Chicago;
IL;
July;
25-28;
1995. L. Yiin is with AT&T Microelectronics;
Allentown;
PA;
18103;
USA;