Space–time block code: Difference between revisions

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This is a very special STBC. It is the '''only''' orthogonal STBC that achieves rate-1.<ref name="sttc" /> That is to say that it is the only STBC that can achieve its full diversity gain without needing to sacrifice its data rate. Strictly, this is only true for [[complex number|complex]] modulation symbols. Since almost all [[constellation diagram]]s rely on complex numbers however, this property usually gives Alamouti's code a significant advantage over the higher-order STBCs even though they achieve a better error-rate performance. See '[[#Rate limits|Rate limits]]' for more detail.
 
The significance of Alamouti's proposal in 1998 is that it was the first demonstration of a method of encoding which enables full diversity with ''linear'' processing at the receiver. Earlier proposals for [[transmit diversity]] required processing schemes which scaled ''exponentially'' with the number of transmit antennas. Furthermore, it was the first [[open-loop]]{{dn|date=March 2017}} [[transmit diversity]] technique which had this capability. Subsequent generalizations of Alamouti's concept have led to a tremendous impact on the wireless communications industry.
 
===Higher order STBCs===