%0 Journal Article
%T Exploiting Spatial and Frequency Diversity in Spatially Correlated MU-MIMO Downlink Channels
%A Rosdiadee Nordin
%J Journal of Computer Networks and Communications
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/414796
%X The effect of self-interference due to the increase of spatial correlation in a MIMO channel has become one of the limiting factors towards the implementation of future network downlink transmissions. This paper aims to reduce the effect of self-interference in a downlink multiuser- (MU-) MIMO transmission by exploiting the available spatial and frequency diversity. The subcarrier allocation scheme can exploit the frequency diversity to determine the self-interference from the ESINR metric, while the spatial diversity can be exploited by introducing the partial feedback scheme, which offers knowledge of the channel condition to the base station and further reduces the effect before the allocation process takes place. The results have shown that the proposed downlink transmission scheme offers robust bit error rate (BER) performance, even when simulated in a fully correlated channel, without imposing higher feedback requirements on the base controller. 1. Introduction Dynamic resource assignment from the Orthogonal Frequency Division Multiple Access (OFDMA) in combination with multiplicative increase in throughput from Multiple-Input Multiple-Output (MIMO) technology offers improved spectral diversity in a wireless downlink transmission. The result of this combination is able to provide a highly efficient and low latency with enhanced spectrum flexibility radio interface, as can be seen from the downlink implementation of a Long Term Evolution (LTE) network [1]. In addition, the LTE network benefits from MU-MIMO, a multiuser diversity technique that exploits the spatial diversity from the channel knowledge at the transmitter, that is, channel state information (CSI), to improve the performance gain. However, accurate CSI is obtained at the expense of massive feedback overhead. A partial feedback scheme, which is based on a quantized discrete Fourier transform (DFT), is considered in this paper. Instead of feeding back the full CSI, mobile users update the E-UTRAN Node B (eNodeB) with the preferred precoding matrix based on the channel quality indicator (CQI). The implementation of the full feedback scheme comes at the expense of CSI; therefore, it requires an enormous amount of feedback to the eNodeB. This scenario is not practical for the downlink implementation because eNodeB requires a higher level of computational overhead to compute the channel matrix. This situation worsens when the channel is severely impaired by channel imperfection, such as spatial correlation, which is also described by Gesbert et al. [2] as an effect of self-interference. This
%U http://www.hindawi.com/journals/jcnc/2012/414796/