name: STTD
full_form: Space Time Transmit Diversity
context: The open loop downlink transmit diversity employs a space time block coding based transmit diversity (STTD). The STTD encoding is optional in UTRAN. STTD support is mandatory at the UE. A block diagram of a generic STTD encoder is shown in the figure 8, figure 8A and figure 8B below. Channel coding, rate matching and interleaving are done as in the non-diversity mode. For QPSK, the STTD encoder operates on 4 symbols b0, b1, b2, b3 as shown in figure 8. For AICH, E-RGCH, E-HICH the are real valued signals, and is defined as . For channels other than AICH, E-RGCH, E-HICH the are 3-valued digits, taking the values 0, 1, "DTX", and is defined as follows: if = 0 then = 1, if = 1 then = 0, otherwise = . Figure 8: Generic block diagram of the STTD encoder for QPSK For 16QAM, STTD operates on blocks of 8 consecutive symbols b0, b1, b2, b3, b4, b5, b6, b7 as shown in figure 8A below. Figure 8A: Generic block diagram of the STTD encoder for 16QAM For 64QAM, STTD operates on blocks of 12
description: Space Time Transmit Diversity (STTD) is a transmit diversity technique used in UTRAN to improve downlink transmission. It employs space-time block coding to provide diversity gain and is optional for the network but mandatory for user equipment (UE). STTD operates on blocks of symbols, with different configurations for QPSK, 16QAM, and 64QAM modulation schemes.
explanation: STTD is classified as a Technology because it involves a specific technique (space-time block coding) used to enhance the performance of a telecommunications system (UTRAN). Its application in improving downlink transmission and its dependence on modulation schemes further solidify its classification as a technological concept.
section_title: 5.3.1.1.1	Space time block coding based transmit antenna diversity (STTD)
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