Generalized Cyclic Delay Diversity for Orthogonal Frequency Division Multiplexing

In this paper, we propose a generalized version of cyclic delay diversity (CDD) which is a popular form of space-frequency coding for multi-antenna orthogonal frequency division multiplexing (OFDM) systems. In this generalized CDD (GCDD) the cyclic delays of CDD are replaced with cyclic diversity filters. Assuming bit-interleaved coded modulation (BICM) for forward error correction, we derive an optimization criterion for the GCDD filters and a gradient algorithm for finding the optimum filters. For certain special cases we also provide a closed-form solution for the optimum filters. Simulation results confirm that GCDD can achieve significant performance gains for conventional CDD, especially in spatially correlated fading.