Özet:

In this paper, the performance of a downlink multiuser zero-forcing (ZF) Vertical Bell Laboratories Layered Space-Time (V-BLAST) with an ordering scheme over Nakagami-m fading channels is presented. A system with two transmit antennas while each user is equipped with r (r≥2) receiver antennas is considered. In every time slot, the base station schedules a single user out of U users and communicates with it by adopting a limited feedback (FB) technique for user scheduling. One user is chosen based on a set of bits each sent from a distinct user to the transmitter. The channel considered in this investigation is the fading channel with Nakagami-m distribution which covers a wide range of multipath fading patterns. The adopted FB scheme requires a threshold value which is attained through a numerical optimization process. For a given shape parameter, the optimum threshold value approaches to zero as SNR increases. The results of the outage probability of the investigated systems with varying m-parameter value of Nakagami-m fading channels are presented and compared with the no FB method. It is shown that the studied FB approach on multiuser ZF V-BLAST indeed outperforms the no FB technique. The shape parameter value clearly affects the performance of the FB system, whereas it seems have no significant effect on the random user scheduling (no FB) method.

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