Transmit Power Allocation for V-BLAST Systems with ZF-OSIC Detection

Abstract

Abstract-This paper proposes a new transmit power allocation (TPA) scheme for the Vertical Bell Layered Space Time (V-BLAST) system with zero-forcing ordered successive interference cancellation (ZF-OSIC) detection. The proposed TPA scheme is based on the minimization of the average probability of vector error subject to a constraint on the total average transmitted power. To derive the TPA algorithm, we consider the asymptotic approximation of the average probability of vector error that is valid at high signal-to-noise ratio. The resulting TPA scheme allocates powers to the transmit antenna elements considering very limited feedback from the receiver. Computer simulations are used to demonstrate the effectiveness of the proposed approach for a V-BLAST system with a maximum of four transmit and receive antenna elements.

Spatial Loading in V-BLAST Systems with Limited Feedback and ZF-OSIC Detection

“…w . As in [7]- [10], the ZF-OSIC detection process at the receiver coincides with that implemented in the conventional V-BLAST, that is, based on the ordered post-detection SNR obtained when P = 1 NT I NT (I k denotes the k × k identity matrix). Therefore, the detection order is not influenced by the transmit power allocation.…”

“…Considering the analysis developed in [3], [12], and [15], it is possible to write the analytic asymptotic approximations of the pdfs at the different detection steps up to N T = 4 and N R = 4. In order to derive their analytic asymptotic approximations at high SNR, in [10] we have extended the analysis developed in [3], [12] for the case of two transmit antennas by taking into account the conjectures used in [15] to analyze the asymptotic outage probability for N R = N T = 3, 4. The asymptotic approximations of the average BERs at the different detection steps can be obtained in the same way we have computed the expressions of the symbol error probabilities at the different detection steps in [10] and by considering that now the instantaneous BER is given by (8).…”

“…Note that, an important characteristic of the two approaches is that of requiring a very limited feedback from the receiver consisting only of the average SNR. The spatial loading problem in V-BLAST systems with ZF-OSIC detection has been investigated in [7]- [10] for the case of power allocation only. A spatial loading algorithm that assigns the data rate and the average power to each transmit antenna so that the instantaneous probabilities of symbol errors are equalized on all the parallel sub-channels has been proposed in [11].…”

“…The resulting spatial loading scheme assigns predetermined data rates and average powers to transmit antenna elements considering a very limited feedback from the receiver that consists of the average SNR and the order in which the sub-streams are detected. As in [5], [6], and [10], the proposed scheme introduces a simplification compared to the other approaches where the information sent by the receiver consists of the average power or the data rate and the average power to be allocated on each transmitter.…”