Soft Cyclic Delay Diversity and its Performance for DVB-T in Ricean Channels

Abstract

Cyclic delay diversity (CDD) provides additional diversity in Rayleigh fading channels, and therefore, improves the system performance. For line-of-sight (LOS) propagation, e.g., the additive white Gaussian noise channel, the implementation of CDD yields to a performance loss. The power distribution among the transmit (TX) antenna branches is a further parameter which can freely be chosen for optimizing the system performance and allows to switch on/off CDD softly. The idea is to feed different power levels into the multiple TX antenna branches rather than distributing the TX power uniformly among the TX antennas. We exemplarily implement the soft CDD principle to the terrestrial digital video broadcasting system (DVB-T). We consider a Ricean multipath fading channel, which allows to control the ratio of LOS and non-LOS propagation power via the Ricean factor for simulations. Simulation results for 2-TX and 4-TX antenna CDD show that antenna power weighting significantly reduces the SNR loss in LOS propagation by the cost of a slight degradation of the SNR gain in non-LOS scenarios.