In this chapter, we consider the problem of transmitting the same copies of information over a wireless channel to a specified subgroup of users that are associated with the transmitter. We assume that the transmitter is equipped with multiple antennas while the users may or may not have multiple antennas. It is observed that when the number of users is small, the max-min beamforming scheme provides some benefit over using OSTBCs. However, as the number of users grows, the performance of this scheme degrades very fast, and at some point, it performs considerably worse than the open-loop OSTBC method. In light of this observation, a MIMO multicasting scheme based on OSTBC precoding is presented.
Improved Space-Time Coding for Multiple Antenna Multicasting, Page 1 of 2
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