On Cyclic Delay Diversity in OFDM Based Transmission Schemes
Source: University of Ulm
Cyclic Delay Diversity (CDD) is a simple approach to introduce spatial diversity to an Orthogonal Frequency Division Multiplexing (OFDM) based transmission scheme that itself has no built-in diversity. It also can be regarded as a Space-Time Code (STC). But in contrast to that there is no additional effort in the receiver necessary, since the different codewords result in a changed channel impulse response in the receiver. This paper investigates CDD for uncoded and coded transmission and show how the inserted diversity can be exploited. Additionally, the paper analyzes how to choose the cyclic shift at each transmit antenna to achieve best possible results, and present a comparison with the well-known Alamouti scheme.