Full-Rate Full-Diversity Achieving MIMO Precoding with Partial CSIT
  In this paper, we consider a $n_t\times n_r$ multiple-input multiple-output (MIMO) channel subjected to block fading. Reliability (in terms of achieved diversity order) and rate (in number of symbols transmitted per channel use) are of interest in such channels. We propose a new precoding scheme which achieves both full diversity ($n_tn_r$th order diversity) as well as full rate ($n_t$ symbols per channel use) using partial channel state information at the transmitter (CSIT), applicable in MIMO systems including $n_r<n_t$ asymmetric MIMO. The proposed scheme achieves full diversity and improved coding gain through an optimization over the choice of constellation sets. The optimization maximizes $d_{min}^2$ for our precoding scheme subject to an energy constraint. The scheme requires feedback of $n_t-1$ angle parameter values, compared to $2n_tn_r$ real coefficients in case of full CSIT. Error rate performance results for $3\times 1$, $3\times 2$, $4\times 1$, $8\times 1$ precoded MIMO systems (with $n_t=3,3,4,8$ symbols per channel use, respectively) show that the proposed precoding achieves 3rd, 6th, 4th and 8th order diversities, respectively. These performances are shown to be better than other precoding schemes in the literature; the better performance is due to the choice of the signal sets and the feedback angles in the proposed scheme. 
Biswajit Dutta, Somsubhra Barik and A. Chockalingam
cs.IT math.IT