Multi-threshold top — full-diversity vector perturbation precodingwith finite-rate feedforward

We consider vector perturbation (VP) precoding for a multiple antenna broadcast scenario with multiple non-cooperative users. Under an instantaneous transmit power constraint, VP precoding requires the feedforward of a power normalization factor to the users. Simple quantization of the power normalization factor is shown to result in an error floor. To overcome this problem, we propose a new precoding scheme that uses a finite set of power normalization factors and avoids transmission at all when the available power is not sufficient to perform channel equalization at the transmit side. With this scheme, full diversity can be achieved (even with imperfect channel state information) while simultaneously significant amounts of transmit power can be saved.