11.5. Uplink transmit diversity

The uplink supports two types of transmit diversity: open- and closed-loop transmit diversity. Both these schemes will be described in this section.

11.5.1. Closed-loop transmit diversity

Closed-loop transmit diversity consists of three different modes. Mode 1 offers codebook-based precoding where the network indicates the preferred precoding vector. All uplink physical channels are subject to precoding, and an additional pilot channel is introduced to facilitate channel sounding. Modes 2 and 3 are based on so-called fixed switched antenna transmit diversity (SATD) where all physical channels are sent from one of the two antennas.5 It is mainly layer-1 processing that is affected by closed-loop transmit diversity. ...

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