What is CDD (cyclic delay diversity)?

Cyclic Delay Diversity (CDD) is utilized in OFDM-based telecommunication frameworks, changing spatial diversity into frequency diversity and thus avoiding intersymbol interference. CDD was presented in 2001 and can acquire frequency diversity at the receiver without changing the SISO receiver design. CDD is a sort of transmit diversity mechanism executed by applying a different phase delay for each OFDM subcarrier. It is utilized in spatial multiplexing to enhance diversity between the 2 spatial paths.