A Scheme of Cyclic Dalay Diversity Based Precoding for Downlink MIMO System

The objective of this paper is to research and analyse the scheme of Cyclic Delay Diversity (CDD) based precoding with two and four transmit antenna on MIMO systems operating in flat and multi-path channel. MIMO precoding is an effective MIMO multiplex mode to improve throughput, and CDD is an efficient transmit diversity scheme suitable for OFDM radio access. In this contribution the principle and system structure of MIMO precoding based on CDD is introduced. The system throughput of the CDD-based precoding with codebook-based precoding according to delay sample, codebook size and RB size for PMI and CQI feedback is evaluated. By choosing a proper cyclic delay between a zero delay (e.g., tau=0) and a small delay(e.g., tau=2), we can efficiently adapt to the proper MIMO mode with a single unified precoding structure.