For many years, the human being has been trying, in all ways, to recreate the complex mechanisms that form the human body. Such task is extremely complicated and the results are not totally satisfactory. However, with increasing technological a

If SDMA is used on the downlink of a multi-user MIMO system, either long-term or short-term channel state information has to be available at the base station (BS) to faciliate the joint precoding of the signals intended for the different users.