Receive Diversity Selection and Switched Diversity
Make use of a number of receive antennas that are well separated (coherence distance) to generate independent receptions of the transmitted signal. Selection diversity: choose received signal with largest received power, S/N, etc. Switched diversity: choose alternate antenna if signal falls below a certain threshold.
Linear combining: linearly combine a weighted replica of all received signals. There is a worthwhile improvement even with two branch selection diversity. Performance improves with the number of diversity branches but the complexity increases sharply.
Selection and Switched Diversity: These are pretty straightforward systems
Space Time Coding – STC Space-Time Diversity Coding.Codes, interleaves and distributes the same symbol over
multiple antennas . Spatial Multiplexing Codes, interleaves and distributes different symbols over multiple antennas. For both, antennas transmit on co-channels
Space-Time Diversity Coding
Using Space-Time Diversity Coding in a multi-path environment increases Rx signal strength, increasing distance.
Distributing the same data over co-channels on spatially displaced antennas, provides a temporally displaced set of sub-streams to be seen by the receiver.