A New Dedicated Pilot Allocation Scheme in Multiuser MIMO OFDM with Vector Perturbation

Multiuser MIMO vector perturbation precoding facilitates multiple representations of the transmit symbols in order to improve transmit power normalization. When reference symbols (pilots) are considered, they must remain unperturbed. For conventional dedicated pilot schemes, where reference and data symbols are separated, the pilot vector is effectively linearly precoded, which degrades the performance. In this paper we propose a new pilot allocation scheme for OFDM systems, where reference and data symbols use the same time/frequency resource and are therefore precoded together to enable this we also present a means for enforcing a zero perturbation restriction upon the perturbation vector for the reference symbols. We support our findings by simulation results for zero-forcing precoding. It is shown that the linearly precoded conventional pilots severely degrade diversity of the system, which can be overcome by our proposed method.