Space–time block coding based transmit diversity
 | This article needs attention from an expert in telecommunications. Please add a reason or a talk parameter to this template to explain the issue with the article. |
Space-time block coding based transmit diversity (STTD) is a method of transmit diversity used in UMTS systems. STTD is optional in the UTRAN but mandatory for user equipment (UE). STTD utilizes Space-time Block Code in order to exploit redundancy in multiply transmitted versions of a signal.
A generic STTD encoder for QPSK creates two sets of STTD encoded symbols which will each be transmitted on two different antennas. If the transmitted symbols consist of b0, b1, b2 and b3, the two tranmitted sets of symbols will consist of b0, b1, b2 and b3 on antenna 1 and !b2, b3, b0 and !b1 on antenna 2.