During the past decade, many wireless communication techniques have been
developedto achievevariousgoals suchas higherdata rate,morerobustlink quality,
and higher number of users in a given bandwidth. For wireless communication
systems, depending on the availability of a feedback link, two approaches can be
considered: namely open and closed loop. Open loop communication system that
does not exploit the channel knowledge at the transmitter is now well understood
from both a theoretical and practical point of view.
